Electricity

Created by

Evi Ashby

Cards (53)

Electrical current is the flow of electrical charge
Charge flow is measured in coulombs
Current is measured in amps or amperes
For an electrical charge, and therefore a current, to flow we need a closed circuit and a source of potential difference.
Current is dependent on resistance and potential difference through the component.
Resistance is measured in ohms.
Potential difference is measured in volts.
If we increase the resistance, we decrease the current.
Current is directly proportional to potential difference.
As the temperature of the filament lamp increases, the resistance increases.
Current only flows through a diode in one direction, because resistance in the reverse direction is very high.
As light intensity in an LDR increases, resistance decreases.
As temperature in a thermistor increases, resistance decreases.
To measure the resistance of a component, you need an ammeter in series to measure current and a voltmeter in parallel to measure potential difference.
Investigate the I-V characteristics of a component [6 marks]
Connect a battery to the component
Add an ammeter in series
Add a voltmeter in parallel
Add a variable resistor in series
Record the potential difference on voltmeter and current on ammeter
Use variable resistor to change pd
Record the new values for pd and current
Repeat the process of changing pd using variable resistor
Reverse power supply connections and repeat process of changing pd
Plot a graph of current against potential difference
In a series circuit, current is the same in each component
In a series circuit, potential difference is shared between components
Total resistance is the sum of resistance of each component
In parallel circuits, current splits between the different loops
In parallel circuits, potential difference is the same in each component
Total resistance in a parallel circuit is less than the resistance of the smallest resistor in the circuit
Why does adding resistors in a series increase total resistance?
The current has more resistors to pass through
Why does adding resistors in a parallel decrease the total resistance?
The parallel loops add an additional path for the current to flow through, so more current can flow in total even when potential difference remains the same
Mains electricity is an alternating current (ac) supply
In an A.C supply, the current repeatedly changes direction, and is produced by an alternating potential difference
Batteries provide a direct current (dc)
In a D.C supply, the current flows in one direction, and is produced by direct potential difference
The mains electricity supply has a frequency of 50 Hz
The mains electricity supply has a potential difference of 230V
In the UK, most electrical appliances are connected to the mains supply using a three-core cable
The live wire is brown, and carries the alternating potential difference from the mains supply, at 230V
The earth wire has green and yellow stripes, and is the safety wire preventing the appliance from becoming live. It only carries a current is there is a fault.
The neutral wire is blue and completes a circuit.
Why do plugs have fuses?
If the current gets too high a thin wire in the fuse melts, breaking the circuit. Prevents risk of electrocution.
The cable grip in the plug holds the wires in place. It's made of plastic as it's a good insulator.
In a plug, the wires are made of copper and coated in plastic. This is because copper is a good conductor and plastic is a good insulator.
Why might a live wire be dangerous even when the switch isn't open?
If you were to touch the live wire, you could complete the circuit (as you are in contact with the ground) and so you could be electrocuted
What is the danger of connecting the live wire to the earth wire?
The circuit would be completed, increasing the risk of electrocution or fires.
Power is measured in watts (W)
The amount of energy transferred by an appliance depends on two factors:
The appliance's power
The amount of time the appliance is on for