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Science P2 Topic 2
Edexcel GCSE additional science physics: electric current
| Question | Answer |
|---|---|
| What is voltage? | Voltage is the energy transferred to a component per unit of charge passed, measured in volts |
| 1 volt = ? | 1 joule per coulomb |
| How is voltage measured? | Using a voltmeter, placed in parallel across the component that is to be measured |
| A higher voltage causes a larger or smaller current? | Larger |
| What is resistance? | A way of measuring how hard it is for electricity to flow, measured in Ohms |
| A higher resistance causes a larger or smaller current? | Smaller |
| What is a light-dependent resistor (how does it work, when is it used)? | It is a resistor that detects light levels (e.g. in automatic security lights),it has a high resistance when it's dark and a low resistance when it's light |
| What is a thermistor (how does it work, when is it used)? | It is a resistor that responds to to changes in heat e.g. it is used in fire alarms to detect warmth- it has a high resistance when it's cold and a low resistance when it's warm |
| What is an I-V curve? | A graph that shows the current plotted against the voltage |
| How do you measure the resistance on an I-V curve? | It is the reciprocal of the gradient of the line |
| What would an I-V curve for a fixed resistor look like and why? | A straight, diagonal line as the current and voltage are in direct proportion to one another (when the resistor is at a constant temperature) |
| What would an I-V curve for a diode look like and why? | Straight line along X axis on one side of Y axis, then a diagonal line upwards on the other side of the Y axis- because diodes conduct electricity in one direction only |
| What would an I-V curve for a filament lamp look like and why? | Gentle curves showing that the current and voltage are not directly proportional- as the resistance increases when the temperature of the filament increases |
| What is power? | The energy transferred per second, measured in watts |
| 1 watt = ? | 1 joule per second |
| Why do resistors warm up when electricity passes through them? | The electrons transfer some of their energy to the ions in the metal lattice making up the resistor, which in turn causes a heating effect |
| What are some advantages/ disadvantages of a heating effect? | Advantages: allows electric fires to heat up, allows kettle to heat water Disadvantages: wastes electricity and money, can cause burns |
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