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P2 – Electricity Pupil Booklet - Foundation Electricity Name……………………………. Teacher..................................... Lab………………………………. 1 P2 – Electricity Pupil Booklet - Foundation Exam Information Date of examination …………………………………………………….. Percentage of GCSE …………………………………………………… Style of examination …………………………………………………….. Length of examination ………………………………………………….. UMS conversion chart A* 45 90 A 40 80 B 35 70 C 30 60 D 25 50 E 20 40 F 15 30 G 10 20 My target grade is……………………. 400 380 360 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 Record of achievement A* A GCSE exams Module UMS B PHY1A C D PHY1B E PHY2 F G PHY3 Learning conversations Date To improve I must………….. 2 Grade ISA Assessment Mark Grade P2 – Electricity Pupil Booklet - Foundation Electricity Assess your knowledge and understanding at different times during this section of the module. Use the following key Describe how insulating materials can become charged using key terms charge and friction Use the golden rules for static electricity to explain how static electricity is used in different situations Describe how a photocopier works Explain how the build up of charge can be dangerous in different situations Describe how the build up of charge can be controlled or prevented Explain how earthing using a conductor can discharge a charged object Describe how the build up of charge can lead to a spark using key terms potential difference, charge and electrons Define electric current Describe how current can be controlled in a circuit using the terms resistance and potential difference Use the equation energy transferred = potential difference x charge State the units of potential difference, current, power, charge, energy , resistance and frequency Use the equation charge = current x time in seconds Recognise the voltage-current graphs for a fixed resistor, filament bulb and diode Use the equation potential difference = current x resistance Interpret the gradient of a voltage-current graph in terms of resistance Calculate resistance from a voltage-current graph Recognise series and parallel circuits State the rules for series and parallel circuits Use the rules for series circuits to calculate potential difference, current and resistance Use the rules for parallel circuits to calculate potential difference and current Recognise all the common circuit symbols including those for the diode, thermistor, light dependent resistor and fuse Draw a voltmeter on a circuit to measure potential difference (in parallel) Draw an ammeter on a circuit to measure current (in series) Read off values of resistance from a graph of light intensity against resistance for a light dependent resistor Read off values of resistance from a graph of temperature against resistance for a thermistor Name and label the different parts of a 3-pin plug State the function of the fuse and cable grip Recognise mistakes in the wiring of a 3-pin plug 3 End Outcome: I should be able to Middle no knowledge or understanding some knowledge or understanding – needs more work confident in knowledge or understanding Start Red: Yellow: Green: P2 – Electricity Pupil Booklet - Foundation Recognise dangerous situations involving mains electricity Use the equation power = current x voltage Use the equation power = current x voltage to calculate normal working current of an electrical device State which fuse to install in an appliance based on normal working current State the danger of installing a fuse of too high a rating Explain how an earth wire protects the user from getting an electric shock if a fault occurs Explain why some devices don’t require an earth wire State UK mains frequency and voltage Mark the time period for one cycle on an oscilloscope trace Calculate frequency using frequency = 1/time period State the units of frequency Describe the difference between alternating and direct current Describe how the potential of the live and neutral terminals vary with respect to each other Calculate peak voltage from an oscilloscope trace Convert values using prefixes such as kilo(k), mega (M), and milli(m). Other prefixes may be used in questions but the examiner will tell you what the prefix means in standard form on the paper NOTE: Equation in bold will not be given, learn it! Frequency = 1/time period for one cycle How Science works Identify independent and dependent variables State whether a variable is discrete, continuous, categoric or ordered Identify control variables Describe how to improve the reliability of results State the range of a set of measurements State the interval between measurements Identify anomalous results and describe how to deal with them Calculate the mean of a set of results Assess the precision of a measuring device Explain how to improve the precision of results Identify directly proportional relationships Identify directly proportional squared relationships Select the correct way to represent results depending on the type of variables used in the experiment – bar chart or line graph Plot points on a graph Draw a line or curve of best fit Explain how to deal with zero errors 4 End Outcome: I should be able to Middle Start These HSW aspects are covered in this booklet. You will need to know more than just these for ISAs. P2 – Electricity Pupil Booklet - Foundation Static Electricity In this lesson, you will learn golden rules for static electricity and how objects become charged. You will then use the golden rules to help explain different phenomena with static electricity. Atomic Structure Understanding static electricity starts with atomic structure. 1. Label the diagram of the atom below. …………………. ………………… . …………………. 2. Complete this table to show the charge and relative mass of each particle within an atom. Particle Charge Relative mass Proton Neutron Electron 3. Write your golden rules for static electricity here. Learn these rules and you will be able to apply this knowledge in questions in the exam. GOLDEN RULES 1. …………………………………………………………………………………………………… 2. …………………………………………………………………………………………………… 3. …………………………………………………………………………………………………… 4. …………………………………………………………………………………………………… 5 P2 – Electricity Pupil Booklet - Foundation How objects become charged 4. When a glass rod is rubbed with a cloth, the glass rod becomes negatively charged. a) Explain how the rod becomes negatively charged. Draw a diagram to help your description. …………………………………………………………… …………………………………………………………… …………………………………………………………… …………………………………………………………… …………………………………………………………… b) What charge is left on the cloth? Explain your answer. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 5. Another rod is rubbed with a different cloth. This time the glass rod becomes positively charged. a) Explain how the rod becomes positively charged. Draw a diagram to help your description. …………………………………………………………… …………………………………………………………… …………………………………………………………… …………………………………………………………… …………………………………………………………… b) What charge is left on the cloth? Explain your answer. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 6. When a computer screen is polished with a cloth, it soon becomes covered in dust again. a) Explain why the dust is attracted towards the computer screen. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………... b) Does it matter if the screen becomes positively or negatively charged? Explain your answer. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 6 P2 – Electricity Pupil Booklet - Foundation 7. If you put your hands on the dome of a Van der Graaff generator your hair stands on end. Explain why. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 8. When you rub a balloon against your hair, your hair sticks to the balloon. Explain why. Assume that the balloon becomes negatively charged. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 9. An insecticide spray gun forces insecticide out through a very fine nozzle. The insecticide droplets become positively charged. a) Explain how the droplets become charged. ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… b) What charge will be on the nozzle of the spray gun and why? ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………………………………………………………………………………………………………… 7 P2 – Electricity Pupil Booklet - Foundation Uses of static electricity How to remove the dirt from smoke Smoke from industrial chimneys such as those at coal fired power stations contains tiny bits of dirt. This dirt falls on houses and gardens. If people breathe in the dirt, it can damage their lungs. The diagram shows how the dirt can be removed from factory chimneys using a smoke precipitator. Explain how the precipitator works. ………………………………………… ………………………………………… ………………………………………… ………………………………………… ………………………………………… ………………………………………… ………………………………………… ………………………………………… ………………………………………… ………………………………………… ……………........................................ How to make a spray hit its target Bicycle frames can be painted using an electrostatic paint spray. Each paint droplet leaves the spray gun with a positive charge. The bicycle frame is given a negative charge. 8 P2 – Electricity Pupil Booklet - Foundation Explain why the paint droplets are all given a positive charge …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… Explain why the bicycle frame is given a negative charge …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… How a photocopier works There is little value in learning how a photocopier works but the exam board still insists on leaving it on the specification for the course. There is no real application of knowledge just a regurgitation of a certain sequence. Learn the sequence of events in case it comes up in the exam! 9 P2 – Electricity Pupil Booklet - Foundation Danger from sparks The most obvious danger of an electrostatic spark is lightning but there are many situations where the build up of charge needs to be either prevented or controlled. You will learn about the measures taken and the theory behind how they work. Refueling petrol tankers and planes 1. What causes the build up of charge on a petrol tanker? ……………………………………………………………………………… ……………………………………………………………………………… 2. What causes the build up of charge on a plane? ……………………………………………………………………………… ……………………………………………………………………………… 3. When fuel is pumped either out of the tanker or into the plane there are fumes that are highly flammable. What could happen if there was a build up of charge on the bodywork? ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… ……………………………………………………………………… 4. Describe and explain how the petrol tanker or plane is made safe before refueling takes place. Highlight the key words in your answer ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 10 P2 – Electricity Pupil Booklet - Foundation Preventing explosions at flour mills I doubt you’ve ever walked into the kitchen, seen a bag of flour and been afraid. However, flour can be very dangerous because it contains a lot of energy. Flour contains complex carbohydrates that are the basis for the energy supplying part of our diets. 1. How does charge build up on the pipe feeding the metal vat? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 2. Why could this be dangerous? …………………………………………………………………………………………………………… 3. Look at the diagram below. Describe and explain how charge is prevented from building up on the pipe and vat. ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… Why does Earthing work? Look at the diagrams and complete the following sentences. When a negatively charged, conducting object is earthed, ______________ move from the object to the earth. When a positively charged object is earthed, electrons move from the __________ to the __________. 11 P2 – Electricity Pupil Booklet - Foundation Making hospital operating theatres safe In a hospital operating theatre, there are several potential dangers A. The drug used to make the patient unconscious is explosive B. There are open wounds C. The air may be treated so that it has a higher than usual oxygen content 1. Explain how the build up of charge could cause each of the potential dangers listed above to become a major problem. A.…………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… B.…………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… C.…………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 2. The operating theatre and the clothes used by hospital staff and patients are designed to reduce risks. Explain each of the following designs for the theatre or clothing by referring to the potential dangers listed above. a) the patient and staff where low friction clothing ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………. b) the patient has a conducting wire attached to their clothing that is then earthed ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… c) the floor is made from a conducting material ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………. 12 P2 – Electricity Pupil Booklet - Foundation From static to current electricity The amount of charge that has flowed in a circuit can be calculated using the equation Charge = (in coulombs) Current (in amps) x time (in seconds) 1. Draw the equipment used to demonstrate changing static electricity to current electricity. 2. What is an electric current? Use key words in your answer. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 3. A current of 1.5A flows through an electric toothbrush for 90 seconds. How much charge has flowed through the toothbrush? ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 4. 350 coulombs of charge flows through an iron in 70 seconds. What is the current flowing through the iron? ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 5. If a current of 2A flows through a bulb for 5 minutes, how much charge has passed through the bulb? ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 13 P2 – Electricity Pupil Booklet - Foundation 6. How long would it take for 2000 coulombs of charge to flow through a motor if the current is 2.5A? ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 7. A wind up radio uses two rechargeable cells, each capable of storing 1800 coulombs of charge. a) For how long can the radio be used without recharging the cells if the radio uses 0.5A of current? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… b) If the owner recharges the cells for 5 minutes, how much charge will be stored in the cells if the total current flowing to the cells is 1.5A? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 8. Roberta and Eugene were trying to work out how much charge there was stored in different electric toothbrush batteries. They measured the current flowing into toothbrush when it was switched on and timed how long it took to run the batteries down. The toothbrush required two batteries. They repeated their experiment twice. Here are their results. Battery Current flowing Time taken (seconds) (Amps) 1 2 3 Longalast 1.15 965 944 957 Durablast 1.25 888 900 768 Morelife 1.20 915 900 909 Charge flowed Mean (Coulombs) a) Circle the anomalous result in the table. b) Calculate the mean average for each brand of battery. c) Calculate the amount of charge stored by each brand of battery. d) How would you present the results of this experiment? Justify your answer. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 14 P2 – Electricity Pupil Booklet - Foundation Modeling Electrical Circuits 1 - Current Modeling electrical circuits can help us to understand the jobs of different components in a circuit and the meanings of terms like current, potential, potential difference, charge and resistance. It is vital that you understand these terms if you are going to understand electrical circuits. 1. In the coal truck model of electrical circuits (above), coal is taken from the coal mine to the power station in trucks on railway lines. Each part of the model represents a part of an electrical circuit. Which part of an electrical circuit is represented by: a) The coal mine? ........................................................................................................... b) The power station? …………………………………………………………………………...... c) The trucks? ........................................................................................................... d) The coal? ........................................................................................................... e) The tracks? ........................................................................................................... 2. How could you represent more current flowing using the power station model? …………………………………………………………………………………………………………...… ……………………………………………………………………………………………………………... 3. What would happen at the power station if more current were to flow? …………………………………………………………………………………………………………...… ……………………………………………………………………………………………………………... 4. How is this similar to an electrical circuit? …………………………………………………………………………………………………………...… ……………………………………………………………………………………………………………... 5. Does the model show current getting used up or not? Explain your answer. …………………………………………………………………………………………………………...… ……………………………………………………………………………………………………………... 15 P2 – Electricity Pupil Booklet - Foundation Modeling Electrical Circuits 2 – Potential Difference The term potential difference sounds new but has a similar meaning to a word you have used before, voltage. In this lesson you will learn what the terms potential, voltage and potential difference mean. And by the way, no eating the Smarties! 1. Draw a diagram of the circuit model you have used. State and explain what each part of the model represents. Indicate where energy is transferred to and from the electrons. ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… 2. Use the model to explain what the term potential difference means and how it is slightly different from voltage or potential. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 3. This model shows how the law of conservation of energy is obeyed in electrical circuits. Explain how the law of conservation of energy is obeyed using this model. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 16 P2 – Electricity Pupil Booklet - Foundation Why do sparks fly? 1. Explain why a spark flies from the dome to the ball using the key words charge, potential difference and electrons. ………………………………………………………… ………………………………………………………… ………………………………………………………… ………………………………………………………… ………………………………………………………… ………………………………………………………… ………………………………………………………… The energy transferred by the charge is measured in joules and can be calculated using the equation: Energy transferred (in joules) = potential difference x (in volts) charge (in coulombs) 3. How much energy is transferred by 3000 coulombs of charge flowing through a bulb with a potential difference of 12V across it? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 4. What is the potential difference across a motor if 100 coulombs of charge transfer 450J of energy? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 5. How much charge needs to flow through a hairdryer to transfer 6.9MJ of energy if the potential difference across the bulb is 230V? ...................................................................................................................................................... ...................................................................................................................................................... 17 P2 – Electricity Pupil Booklet - Foundation 6. Lightning is caused by the build up of charge within a thunder cloud. a) Explain why a lightning bolt occurs. Use key words in your answer. ………………………………………………………………………… ………………………………………………………………………… ………………………………………………………………………… ………………………………………………………………………… b) There is a potential difference of 6MV between the cloud and the ground. If a lightning bolt strikes and transfers 12KJ of energy, how much charge has flowed during the strike? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… Controlling Current in Circuits Draw the circuit diagram for the circuit you set up. Explain how you controlled the current in the circuit. ………………………………………………… ………………………………………………… ………………………………………………… ………………………………………………… ………………………………………………… Resistance, potential difference and current are linked by this equation: Potential difference (in volts) = current (in amps) x resistance (in ohms,Ω) 18 P2 – Electricity Pupil Booklet - Foundation Circuit Symbols Match the symbol to the component and its function. Symbol Component Function ammeter Measures potential difference battery Resists the flow of current cell Lights when a current flows through it voltmeter Measures the current flowing filament lamp Provides energy to the circuit light dependent resistor Provides energy to the circuit resistor Varies the resistance of a circuit variable resistor Breaks the circuit if too much current flows fuse Its resistance changes with temperature diode Only allows current to flow through it one direction Its resistance changes with light intensity thermistor 19 P2 – Electricity Pupil Booklet - Foundation How does the length of wire affect the resistance of the wire? In this investigation, you are going to increase the length of wire in a circuit and see how it affects the resistance of the wire. 1. The independent variable is ………………………………………………………………………………. 2. This variable is categoric/continuous/discrete/ordered 3. The independent variable is ………………………………………………………………………………. 4. This variable is categoric/continuous/discrete/ordered. 5. State two control variables ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………….. Results Length of wire Potential difference across Current flowing through wire Resistance (cm) the wire (volts) (amps) (Ω) 0.0 1 2 Mean 1 2 Mean 0.00 0.00 0.00 0.00 0.00 0.00 0.00 20.0 40.0 60.0 80.0 100.0 6. Circle any anomalies and calculate the mean results and resistances. 7. What is the relationship between the length of wire and the resistance of the wire? ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 8. What range of lengths of wire did you use? Include the unit………………………………………… 9. What interval did you use for the lengths of wire? …………………………………………………….. 10. To what precision did you measure the length of wire? ………………………………………………. 11. Draw a line graph of your results. Stick your graph on the next page. 20 P2 – Electricity Pupil Booklet - Foundation 12. Use your graph to estimate the resistance of the wire when its length is 55cm …………………… 13. How much current would flow through a 55cm length of wire when a potential difference of 5V is across the wire? ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 14. Read the following passage and then explain why the resistance of the wire increases as the length increases. ‘As free electrons flow through a wire they collide with ions in the metal lattice. This causes the free electrons to transfer some energy to the wire as heat and the free electrons slow down. These collisions are what cause resistance in a wire.’ ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 21 P2 – Electricity Pupil Booklet - Foundation Voltage-current graph for a fixed resistor 1. Draw the circuit diagram for this experiment Potential Difference (V) 1 2 Mean Current (A) 1 2 Resistance (Ω) Mean 2. What can you say about the resistance as the potential difference across the resistor increases? ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 3. Write a conclusion about the relationship between potential difference and current. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 4. You should draw a line graph of these results? Why? ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 5. Plot a line graph of your results. Plot potential difference along the x axis and current along the yaxis. 6. Why is the potential difference plotted on the x-axis? ………………………………………………………………………………………………………………. 7. Circle any anomalies on your graph. 8. To what precision was the potential difference measured? …………………………………………… 9. To what precision was the current measured? ………………………………………………………… 10. What range of potential differences did you use? ……………………………………………………… 22 P2 – Electricity Pupil Booklet - Foundation 11. Stick your graph here. 12. Calculate the gradient of your line. Remember gradient = change in y axis ÷ change in x-axis. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 13. What does the gradient of the line represent? Look at what you have plotted on the axes and how you calculated the gradient to help you. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 14. Draw the line you would expect to see for a resistor of twice the resistance of your resistor. Label the line ‘twice the resistance’ 15. Draw the line you would expect to see for a resistor of half the resistance of your resistor. Label the line ‘half the resistance’ 23 P2 – Electricity Pupil Booklet - Foundation Voltage-current graph for a filament lamp 1. Draw the circuit diagram for this experiment Potential Difference (V) 1 2 Mean Current (A) 1 2 Resistance (Ω) Mean 2. What can you say about the resistance as the potential difference across the filament increases? ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 3. Why do you think this has happened? Look at your conclusion to the last experiment ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 4. Write a conclusion about the relationship between voltage and current. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 5. Should your draw a bar chart or line graph of these results? Justify your answer. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 6. Draw your bar chart or line graph. 7. Circle any anomalies in your table or on your graph. 8. If the ammeter you used had a zero error of 0.02A, what would you do to eliminate this error? ………………………………………………………………………………………………………………... ……………………………………………………………………………………………………………....... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... 24 P2 – Electricity Pupil Booklet - Foundation Stick your bar chart/line graph here. Diodes Diodes are used in many different circuits depending on the need. For example, light emitting diodes (LEDs) are used to indicate that something is working. Other diodes are used to protect your computers and to change alternating current to direct current. 1. In which of these circuits would the filament lamp be on? ………………………………………… 25 P2 – Electricity Pupil Booklet - Foundation 2. Draw the circuit diagram for this demonstration Potential Difference (V) Current (A) Resistance (Ω) 3. Sketch the voltage-current graph for a diode. Label important points on the graph. Summary Sketch the four quadrant graphs for a fixed resistor and a filament lamp on the axes below. 26 P2 – Electricity Pupil Booklet - Foundation Series and parallel circuits In the examination, the first thing that you will need to do to be able to answer a question on circuits is to identify whether the circuit is series or parallel. You will then need to apply the rules for each type of circuit and you can then answer any question. 1. What is special about a series circuit? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 2. What is special about a parallel circuit? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… Series Circuits 3. Draw the circuit diagram and tables on the board. 4. What conclusion can you come to about the current flowing in a series circuit? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 5. What is the relationship between the supply potential difference and the potential differences across the bulbs? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 6. Calculate the resistance of each bulb. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. 7. State the total resistance of the circuit …………………………………………………………….... 27 P2 – Electricity Pupil Booklet - Foundation Series Circuit Calculations 1. Each cell in this circuit provides 3V. a) What is the total potential difference provided by the cells? ………………………………………………………… b) Bulb A has a resistance of 2 ohms. Calculate the potential difference across bulb A. ………………………………………………………… ………………………………………………………… c) What is the potential difference across bulb B? ………………………………………………………… d) Calculate the resistance of bulb B ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… e) Why do you think there is twice the potential difference across bulb A compared to bulb B? ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… 2. The cells in this circuit are identical. a) How much potential difference is provided by the each cell? ………………………………………………………… b) Calculate the total resistance of the bulbs. ………………………………………………………… ………………………………………………………… c) The bulbs are identical. i) What is the resistance of each bulb? …………………………………………………………………………………………………………….. ii) What potential difference would you expect to see across each bulb? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 28 P2 – Electricity Pupil Booklet - Foundation Parallel Circuits 1. Draw the circuit diagram and tables on the board. 2. What conclusion can you come to about the potential difference across each branch of a parallel circuit? …………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. 3. What is the relationship between the current flowing in each branch of a parallel circuit and the total current flowing in the circuit? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 4. Which bulb in you experiment do you think had the highest resistance? Explain your reasoning. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… Summary Golden rules Series circuits Parallel circuits 1 1 2 2 3 3 29 P2 – Electricity Pupil Booklet - Foundation Parallel Circuit Calculations 1. The two resistors in this circuit have different resistances. a) How much current flows through resistor B? ……………………………………………………… b) Calculate the resistance of resistor A. ………………………………………………………… ………………………………………………………… c) Calculate the resistance of resistor B. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… d) Why do you think twice as much current flows through resistor A compared to resistor B? ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………….. 2. Bulbs A, B and C are identical. a) How much current will flow through bulb A? ………………………………………………………… b) Calculate the resistance of bulb A. ………………………………………………………… ………………………………………………………… c) How much potential difference will be across bulb B? ………………………………………………... d) Calculate the resistance of bulb C. ……………………………………………………………………………………………………………….. Extension e) What is the total resistance of this circuit? Tricky question! ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………. 30 P2 – Electricity Pupil Booklet - Foundation Sensing the environment The output of an electrical device can be changed by changing the resistance in the circuit. The resistance can be changed manually by pressing a button or using a remote control but many electrical devices change their output by sensing their environment. 1. Write down as many environmental factors as you can that may be sensed by an electrical device. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… Light Dependent Resistors 2. Draw the circuit diagram for this experiment. Pieces of tracing paper Resistance (kΩ) 1 2 Mean 0 1 2 3 4 5 3. What is the relationship between light intensity and resistance of the light dependent resistor? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 4. Write down as many uses of light dependent resistors as you can think of. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 31 P2 – Electricity Pupil Booklet - Foundation Thermistors 5. What do thermistors detect? …………………………………………………………………………………………………………… 6. Draw the circuit diagram for this experiment. Temperature (oC) Resistance (kΩ) 20.0 35.0 50.0 65.0 80.0 95.0 7. What is the relationship between temperature and the resistance of this thermistor? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 8. Draw a graph of temperature against resistance for this thermistor and stick it in here. 32 P2 – Electricity Pupil Booklet - Foundation 9. A heating engineer wants to design his electronic circuit to switch on when the temperature reaches 50 oC. a) What is the resistance of this thermistor at 50 oC? Draw your construction lines on your graph. …………………………………………………………………………………………………….. b) Calculate the current that would flow through this thermistor at 50 oC. The thermistor operates with a 2V potential difference across it. …………………………………………………………………………………………………….. ……………………………………………………………………………………………………... ........................................................................................................................................... 10. A reptile tank manufacturer wants to switch off the heater to a tank when it reaches 30 oC. a) What is the resistance of this thermistor at 30 oC? Draw your construction lines on your graph. ……………………………………………………………………………………………………. b) Calculate the current that would flow through this thermistor at 30 oC. The thermistor operates with a 2V potential difference across it. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. ……………………………………………………………………………………………………. 11. What range of temperatures was used in this experiment? ………………………………………. 12. What interval was used for the temperature? ………………………………………………………. 13. To what precision was the temperature measured in this experiment? ……………………………………………………………………………………………………………. 14. To what precision was the resistance measured in this experiment? Show your working. …………………………………………………………………………………………………………..… …………………………………………………………………………………………………………..… …………………………………………………………………………………………………………….. 15. Is the relationship between temperature and resistance inversely proportional for this thermistor? Show your working. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 33 P2 – Electricity Pupil Booklet - Foundation Mains electricity On average, there are about 100 deaths due to electrocution annually in the UK. This is because it only takes a small electric shock to kill a human being. So, we have to be very careful when dealing with mains electricity. Why A.C. electric shocks are so dangerous 1. What are the two main factors that affect how lethal an electric shock is? ……………………………………………………………………………………………………………... 2. What happens to the heart if an alternating current passes through it? …………………………………………………………………………………………………………..…. ……………………………………………………………………………………………………………... ...................................................................................................................................................... 3. What size of alternating current can be fatal if it passes through the heart? ……………………... Connecting to the mains 1. Label the parts of this 3-pin plug. ……………………... ……………………... ……………………... ……………………... ……………………... 2. What colour is the a) Live wire? ………………………………………………………………………………………… b) Neutral wire? …………………………………………………………………………………….. c) Earth wire? ………………………………………………………………………………………. 34 P2 – Electricity Pupil Booklet - Foundation 3. What is the function of the fuse? ……………………………………………………………………………………………………………... ...................................................................................................................................................... 4. What is the function of the cable grip? …………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………... 5. Why is the earth pin longer than the live and neutral pins? …………………………………………………………………………………………………………..… …………………………………………………………………………………………………………..… Which fuse to use? When too much current flows through the fuse in a 3-pin plug the fuse wire gets hot, melts and breaks the circuit. But how much current is too much current? It’s easy to work out how much current should be flowing through a device and hence which fuse should be placed in the plug. To work out how much current normally flows through a device use this equation: Current = (in amps) Power ÷ (in watts) Voltage (in volts) 1. How much current normally flows through a 2000W kettle that works on mains voltage (230V)? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. 2. Select the appropriate fuse to install in the plug for this kettle 1A 3A 5A 13A 3. Calculate the normal current flowing in a 690W microwave oven …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. 4. Select the appropriate fuse to install in the plug for this microwave 1A 3A 5A 35 13A P2 – Electricity Pupil Booklet - Foundation Unsafe plugs PLUG Why is it unsafe? 36 What needs to be done? P2 – Electricity Pupil Booklet - Foundation Earthing 1. Through which two wires does current flow in and out of the device? ……………………………………………………………………………………………………………. 2. The diagram below shows the layout of a kettle with a fault where the earth wire is not connected. The outer case of the kettle has now become live. If touched by someone they could get electrocuted. Colour in red the route that the current takes when the person gets a shock. 3. Redraw the diagram (smiley face this time) with an Earth wire connected to the inside of the metal case. Colour the path that the current now takes in red. 37 P2 – Electricity Pupil Booklet - Foundation 4. Why does the vast majority of the current flow through this path? …………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. 5. What happens to the fuse when it ‘blows’? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 6. Why does the fuse ‘blow’ when there is a fault but not when the kettle is working normally? …………………………………………………………………………………………………………… ……………………………………………………………………………………………………………. 7. Many devices do not require an Earth wire. Why not? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 8. Devices with plastic cases are called ‘double insulated’. What do you think this means? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… Extension 9. Current flows into a device through the live wire and out through the neutral wire. Look at the diagram of the kettle and explain why it is very dangerous to wire the live and neutral the wrong way round. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 38 P2 – Electricity Pupil Booklet - Foundation Ed the electrician Ed the electrician is a bit of a cowboy. He’s picked up a consignment of dodgy cable from a shady character in a local pub at half price. When he gets it back to his shed he finds that the cable only has two wires, the live and neutral. When Ed goes back to the pub he finds that the bloke has gone and nobody seems to know him. Ed paid in cash and knows that he’s lost his money. Ed decides to use the cable for his wiring anyway. Write a letter to Ed explaining the possible dangers of using this cable. …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 39 P2 – Electricity Pupil Booklet - Foundation A.C./D.C what does it all mean? In this lesson, you will learn how mains electricity is different from the electricity from cells. You will also learn how to interpret mains traces and calculate peak voltages and frequency. 1. What do the terms a.c. and d.c. mean? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 2. What is the difference between a.c. and d.c.? …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 3. Which type of current is supplied by mains electricity? …………………………………………… 4. Which type of current is supplied by cells? ………………………………………………………… 5. Use the circuits below to describe how the potential of the live and neutral terminals in a 3-pin plug vary. L N L N …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 6. Draw the traces to show how the live and neutral potentials vary through one cycle. Label the axes. 40 P2 – Electricity Pupil Booklet - Foundation Frequency and peak voltage 1. What does frequency mean? ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… 2. What is mains frequency? ……………………………………………………………………………… 3. What is mains voltage? ………………………………………………………………………………… 4. The frequency of a supply can be calculated using this equation Frequency = 1/time period for one cycle (in hertz) (in seconds) a) Label one time period (cycle) on the diagram below b) If the time base setting is 0.10 seconds, calculate the frequency for this supply. …………………………………………………………………………………………………………… ……………………………………………………………………………………..……………………… …………………………………………………………………………………………………………… 41 P2 – Electricity Pupil Booklet - Foundation Problems 1 An a.c. source is connected to an oscilloscope. The waveform of the alternating potential difference from the source is displayed on the oscilloscope screen as below. a) The Y-gain setting of the oscilloscope is 0.5 V/cm. Determine the amplitude of the alternating potential difference. .................................................................................................................................................. .................................................................................................................................................. b) The time-base setting of the oscilloscope is 0.02 seconds per cm. i) Show that the time for one cycle of the waveform is 0.06 s. ............................................................................................................................................ ............................................................................................................................................ ii) Calculate the frequency of the alternating potential difference. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ 42 P2 – Electricity Pupil Booklet - Foundation 2 An a.c. source is connected to an oscilloscope. The waveform of the alternating potential difference from the source is displayed on the oscilloscope screen as below. a) The Y-gain setting of the oscilloscope is 2.0 V/cm. Determine the amplitude of the alternating potential difference. .................................................................................................................................................. .................................................................................................................................................. b) The time-base setting of the oscilloscope is 0.010 seconds per cm. Determine the frequency of the alternating potential difference. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. c) The a.c. supply is disconnected and a horizontal flat trace across the middle of the screen is seen. On the screen above, draw the trace that you would expect to see if the a.c. supply was replaced by a battery of p.d. 3.0 V. 43 P2 – Electricity Pupil Booklet - Foundation …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 44 P2 – Electricity Pupil Booklet - Foundation …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 45 P2 – Electricity Pupil Booklet - Foundation …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 46 P2 – Electricity Pupil Booklet - Foundation …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 47 P2 – Electricity Pupil Booklet - Foundation …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… 48