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Transcript
1) a) b) c) Current is the rate of flow of….. Energy Charge protons Answer b) Charge Bonus What is the unit of current? Answer Amps, A 2) Voltage (potential difference) is the ……..? a) Energy transferred per unit charged passed b) The rate of charge per second c) Current transferred per unit charged passed a) Energy transferred per unit charged passed The driving force that pushes the current around Bonus What is the unit for Voltage? Answer Volts, V (or a Joule / Coulomb, J/C) 3) 1 volt is equal to… a) 1 joule/charge b) 1 joule/coulomb c) 1 Joule/amp b) 1 joule/coulomb 4) Resistance is…..; a) Rate of flow of charge b) Anything that slows down the flow of current. Answer b) Anything that slows down the flow of current. Bonus What is the unit of resistance? Answer Ohms, Ω 5) The bigger the voltage supplied to a circuit… a) The more the energy b) The less the energy Answer a) The more the energy. 6) At junction in a circuit the current is…. a) Split b) Stays the same a) Split 7) 6) At junction in a circuit the voltage is…. a) Split b) Stays the same Ans: b) Stays the same 8). Ammeter in a circuit measures …. a) Voltage b) Current c) Resistance Ans: Current Bonus: An ammeter is placed in…. a) Series b) In parallel Bonus: An ammeter is placed in…. a) Series 9) Voltmeter in a circuit measures …. a) Voltage b) Current c) Resistance . Ans:. a) Voltage Bonus: An Voltmeter is placed in…. a) Series b) In parallel Bonus: An ammeter is placed in…. a) Parallel around the component 10) What is a variable resistor used for? Ans: • Changes the resistance of the circuit which in turn changes the current 11) What are the three voltage-current graphs that must be known (3) Ans: a) Fixed resistor b) Filament bulb c) Diode 12) Describe using a graph how the current varies with the voltage in a fixed resistor. Ans: Current Voltag e 1. Resistor (Constant temp) Current increases in proportion to voltage 13) Describe using a graph how the current varies with the voltage in a filament bulb? Ans: . Current Voltag e 2. Bulb (Filament Lamp) As voltage increases the bulb gets hotter and resistance increases, current levels off 14) Describe using a graph how the current varies with the voltage in a diode? (2) Ans: Current Voltag e 3. Diode A diode only lets current go in one direction – it has very high resistance in the other direction 15) What is the formula that links current and voltage? (2) Ans: V= I X R Potential difference = Current X Resistance 16) What is a LDR ? (2) Ans: • It is a light dependent resistor • It’s a resistor that changes its resistance according to the amount of light it receives. 17) Use a graph to describe how the resistance varies with the light ? (2) Ans: In bright light the resistance falls-so curent increases In darkness , the resistance is the highest Resistance 1) Light dependant resistor – resistance DECREASES when light intensity INCREASES Amount of light 18) Use a graph to describe how the resistance varies with the temperature in a thermistor? (2) Ans: In hot conditions the resistance falls-so current increases. In cool conditions , the resistance goes up. Resistance 2) Thermistor – resistance DECREASES when temperature INCREASES Temperature 19) Why does an electric component (resistor) become hot when current passes through it ? (2) Ans: • There is energy transfer so resistor heats up. • Energy transfer is because • electrons collide with ions in the lattice as they move through it. • These collisions give ions extra energy which is emitted as heat. 20) Heating effect …… a) Increases the resistors resistance so less current will flow. b) Decrease the resistors resistance so less current will flow. c) Decrease the resistors resistance so more current will flow. Ans: a) Increases the resistors resistance so less current will flow. 21) Heating effect can cause …… a) Can make electrical devices more efficient because less energy is wasted as heat. b) Can make electrical devices less efficient because more energy is wasted as heat. c) Has no effect on the efficiency of the device. Ans: b) Can make electrical devices less efficient because more energy is wasted as heat. 22) Give an example of how the heating effect of an electric current can be useful. Ans: • Electric toaster or heater. • Toaster or heater contains a coil with very high resistance. • When a current flow through the coil, temperature shoots up, leading to infra-red radiation being given off. • Infra-red radiation cooks the bread in the toaster. 23) What is the equation which links electrical power with current and voltage?. Ans: • Electrical power = potential difference x current Bonus • What is the definition of electric power? Answer • The rate at which energy is transferred in an appliance? 24) High power appliances … a) Draw small currents b) Large currents Ans: b) Large currents Bonus What is the unit for power? Answer Watts (W) 25) What is the equation that links energy transferred, current, voltage and time Ans: Electrical energy = Current X Potential difference X Time Electrical energy = IxVxt Bonus The energy transferred by a component is dependent on …. Answer The current through it, the voltage supplied and how long it is on for measured in seconds.