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gcse science P4 - C
specific for ocr gateway additonal science B.
| Question | Answer |
|---|---|
| what is an electric current? | a flow of electric charge |
| what is charge carried by? | negatively charged electrons |
| what direction do the electrons flow in a circuit? | the opposite direction to the current |
| what is current measured in? | amperes (A) |
| what is used to measure current? | ammeter connected in series |
| what is the current in a circuit due to? | electron movement |
| how does this work? | -electrons are pushed around the circuit by the battery -they bump into atoms in the resistor, giving the electrons energy -their energy makes the atoms vibrate more, so the resistor gets hotter and its resistance increases |
| what changes the resistance? | a variable resistor (rheostat) |
| what increases the current? what decreases the current? | -a low resistance -a high resistance |
| what is the potential difference(pd)between two points in a circuit? | the difference in voltage between the two points |
| what is potential difference measured in? | volts (v) |
| what is used to measure the potential difference? | voltmeter connected in parallel |
| what happens if the voltage increases? | the current increases |
| what happens if the resistance increases? | the current decreases |
| what is resistance measured in? | ohms (Ω) |
| what does the live wire do? | carries a high voltage around the house |
| what colour is the live wire? | brown |
| what does the neutral wire do? | completes the circuit, providing a return path for the current |
| what colour is the neutral wire? | blue |
| what does the earth wire do? | connected to the case of an appliance to prevent it becoming live |
| what colour is the earth wire? | green and yellow stripes |
| what does the fuse do if the current becomes too large? | melts and breaks the circuit, so no current can flow. this prevents overheating and further damage to the appliance |
| how do earth wires and fuses prevent a person from receiving and electric shock if they touch a fault appliance? | as soon as the case becomes live, a large current flows in the earth and live wires, and the fuse blows |
| why doesn't a re-settable fuse (circuit breaker) need to be replaced to restore power? | it can be re-set |
Created by:
jirwin
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