# Physics - P2 Tpoic 2 - Controlling and using electric current

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• P2 Topic 2 - Controlling and using electric current
• Key terms
• current
• the rate of flow of charge
• voltage
• what pushes the current around the circuit
• resistance
• something that slows the current down
• the balance
• if you increase the voltage, then more current will flow
• potential differance
• voltage = current x time
• Energy transferred
• when electric charge goes through a change (gives up energy) of potential difference
• electrical power = potential difference x current
• energy transferred = current x potential difference x time
• Energy conserved
• junctions
• where the current either splits or rejoins in a parallel circuit
• current doesn't get used up or lost in a circuit
• its conserved
• the total current entering the junction is the same as the total leaving the junction
• its conserved
• Resistance
• ammeter
• measures current - must be placed in series
• voltmeter
• measures voltage - must be placed in parallel around the component
• voltage-current graphs
• fixed resistors
• current is proportional to voltage
• filament lamps
• as temperature increases, resistance increases
• diode
• current will only flow in one direction
• Devices and reisitance
• light dependent resistor
• in bright light resistance falls
• thermistor
• in hot weather, resistance drops
• resistors
• get hot when an electric current passes through them
• electrons collide with ions in the lattice
• heat causes resistance to increase
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