The Basics
DC: Direct Current: A battery has two terminals- a positive and a negative.When a battery is in use, current flows from the positive terminal of the battery around the circuit back to the negative terminal in one direction.
DC supply switch closed
AC: Alternating current- The voltage of the mains is much higher than the voltage of a battery and the current flowing changes direction 50 times a second.
AC supply- switch open
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Current amperes A |
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Voltage volts V |
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Power watts W |
An electric current is a flow of electric charge - electrons flowing from the negative terminal ( cathode) of a battery to the positive terminal ( anode). Electricity will flow if there is a potential difference and a complete circuit.
Potential difference
In all electric circuits energy is supplied by the energy source such as the battery or mains. This energy source has an electromotive force (EMF), which produces a potential difference (Voltage) across the circuit. The voltage is a measure of the strength of the power supply.
Resistance
Resistance is the ratio of potential difference across a conductor to the current flowing through it.
If energy is used in passing electricity through an object, that object has a resistance.