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# Science P2 Topic 2

### Edexcel GCSE additional science physics: electric current

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
Created by: 11043