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Electric current
Beginner
Rate of flow of charge.
I = dQ/dtCurrent is the rate of flow of charge past a point: I = dQ/dt, in amperes (1 A = 1 C/s). In metals it is carried by electrons; in electrolytes by ions.
A phone charger at 2 A moves 2 C each second.
Current is a scalar with a conventional direction.
In more detail
Electric current is the rate of flow of charge through a conductor, I = dQ/dt, measured in amperes. One ampere is one coulomb per second.
Real-world uses
- Household appliances are rated by the current they draw.
- Fuses are chosen to break the circuit before current becomes dangerous.
- A phone charger delivers a steady current of a few amperes into the battery, which sets how quickly the battery charges.
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Frequently asked questions
What is a typical household current?
A few amperes for lights and appliances, and tens of amperes for large loads like cookers.
Does current get used up in a circuit?
No. The same current flows through each part of a series circuit.
Is current used up in a circuit?
No. Charge flows round the circuit, and the same current passes through every component in a series loop.