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gcse science P4 - C

specific for ocr gateway additonal science B.

QuestionAnswer
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