What must be applied to an electric charge to make it flow in a circuit?

Answer 1

There are many complex explanations for current flow in electronics. The answer below describes the basic requirements without including great detail. For a more academic discussion, you are advised to look at relevant sections of text books on electrical and electronic engineering.

In order for electrical current to flow, there must be two things:

1) A voltage (sometimes referred to as a "potential difference"). The voltage can be created by a battery, a generator, a solar cell or a mains voltage outlet.

2) A complete circuit. This must include conductors such as wires that start at the positive terminal of the voltage source and at the far end, return to the negative terminal of the voltage source. Other components such as lamps, resistors and switches can form part of the complete circuit.

We must have a voltage for current to flow because without it, there is no "electrical force" to cause the current to flow.

We need a complete circuit so that the current can flow from the positive of the voltage source, through conductors and return to the negative of the voltage source. Current will flow through any complete circuit. If a switch is part of the circuit, when it is open, no current can flow because the circuit has been broken. When the switch is closed, the circuit is complete and current will flow once again.

Therefore, it is possible to have a voltage without a current (switch open, for example) but it is not possible to have a current without a voltage.

NB: Mains electricity is alternating current. It follows the same principles as the DC examples mentioned above although there is a changing voltage rather than a constant voltage.

Answer 2

A potential difference - also known as a voltage or an EMF (Electro-motive force) - must be applied across the connection points to the circuit to make electrical charge flow in that circuit.

Answer 3

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