* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download What you will need to remember from year 10…
Nanofluidic circuitry wikipedia , lookup
Josephson voltage standard wikipedia , lookup
Thermal runaway wikipedia , lookup
Negative resistance wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Galvanometer wikipedia , lookup
Schmitt trigger wikipedia , lookup
Power electronics wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Operational amplifier wikipedia , lookup
Wilson current mirror wikipedia , lookup
Electrical ballast wikipedia , lookup
Power MOSFET wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Surge protector wikipedia , lookup
Current source wikipedia , lookup
Rectiverter wikipedia , lookup
Network analysis (electrical circuits) wikipedia , lookup
Energy and Electricity Basic ideas… Electric current is when electrons start to flow around a circuit. We use an _________ to measure it and it is measured in ____. Potential difference (also called _______) is how big the push on the electrons is. We use a ________ to measure it and it is measured in ______, a unit named after Volta. Resistance is anything that resists an electric current. It is measured in _____. Words: volts, amps, ohms, voltage, ammeter, voltmeter Current in a series circuit If the current here is 2 amps… The current here will be… The current here will be… And the current here will be… In other words, the current in a series circuit is THE SAME at any point Current in a parallel circuit A PARALLEL circuit is one where the current has a “choice of routes” Here comes the current… Half of the current will go down here (assuming the bulbs are the same)… And the rest will go down here… Current in a parallel circuit If the current here is 6 amps And the current here will be… The current here will be… The current here will be… The current here will be… Voltage in a series circuit If the voltage across the battery is 6V… V …and these bulbs are all identical… …what will the voltage across each bulb be? V V 2V Voltage in a series circuit If the voltage across the battery is 6V… …what will the voltage across two bulbs be? V V 4V Voltage in a parallel circuit If the voltage across the batteries is 4V… What is the voltage here? 4V V And here? V 4V Summary In a SERIES circuit: Current is THE SAME at any point Voltage SPLITS UP over each component In a PARALLEL circuit: Current SPLITS UP down each “strand” Voltage is THE SAME across each”strand” An example question: 6V A3 3A A1 V1 A2 V2 V3 Advantages of parallel circuits… There are two main reasons why parallel circuits are used more commonly than series circuits: 1) Extra appliances (like bulbs) can be added without affecting the output of the others 2) If one appliance breaks it won’t affect the others either Resistance Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. Georg Simon Ohm 1789-1854 The resistance of a component can be calculated using Ohm’s Law: Resistance (in ) = V Voltage (in V) Current (in A) I R An example question: Ammeter reads 2A A V Voltmeter reads 10V 1) What is the resistance across this bulb? 2) Assuming all the bulbs are the same what is the total resistance in this circuit? More examples… 3A 6V 12V 3A 2A 4V 2V 1A What is the resistance of these bulbs? Two simple components: 1) Light dependant resistor – resistance DECREASES when light intensity INCREASES Resistance 2) Thermistor – resistance DECREASES when temperature INCREASES Resistance Amount of light Temperature Current-voltage graphs I I I V V V 1. Resistor Current increases in proportion to voltage 2. Bulb As voltage increases the bulb gets hotter and resistance increases 3. Diode A diode only lets current go in one direction DC and AC + DC stands for “Direct Current” – the current only flows in one direction: V Time - AC stands for “Alternating Current” – the current changes direction 50 times every second (frequency = 50Hz) 1/50th s + 240V T - V Fuses Fuses are _______ devices. If there is a fault in an appliance which causes the ____ and neutral (or earth) wire to cross then a ______ current will flow through the _____ and cause it to _____. This will break the _______ and protect the appliance and user from further _____. Words – large, damage, safety, melt, live, circuit, fuse Other safety devices… 1) Insulation and double insulation Insulating a wire prevents someone from touching the ____ wire. A device can also be double insulated – this is when the metal parts inside the device are insulated from the outer case. A double insulated device does not need an _______ wire but they still have _____. 2) Residual Current Circuit Breaker This circuit breaker detects any difference in current between the live and neutral connectors and switches off the current when needed. They can be easily _______. Words – earth, reset, live, fuses The Cost of Electricity Electricity is measured in units called “kilowatt hours” (kWh). For example… A 3kW fire left on for 1 hour uses 3kWh of energy A 1kW toaster left on for 2 hours uses 2kWh •A 0.5kW Vacuum Cleaner left on for 4 hours uses __kWh •A 200W TV left on for 5 hours uses __kWh •A 2kW kettle left on for 15 minutes uses __kWh The Cost of Electricity To work out how much a device costs we do the following: Cost of electricity = Power (kW) x time (h) x cost per kWh (p) For example, if electricity costs 8baht per unit calculate the cost of the following… 1) A 2kW fire left on for 3 hours 48B 2) A 0.2kW TV left on for 5 hours 8B 3) A 0.1kW light bulb left on for 10 hours 8B 4) A 0.5kW hoover left on for 1 hour 4B