Current, Charge and Potential Difference

This lesson covers the fundamental electrical quantities — current, charge and potential difference — as required by AQA GCSE Combined Science Trilogy (8464, section 6.2.1). These three quantities and the relationships between them form the foundation for every electricity topic at GCSE.

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Electric Current

Electric current is the rate of flow of electric charge. In metallic conductors (such as copper wires), the charge carriers are electrons. In electrolytes (solutions that conduct), the charge carriers are ions.

Current is measured in amperes (A) using an ammeter, which is always connected in series with the component being measured.

The Charge Equation

$Q = I \times t$Q=I×t

Where:

• $Q$Q = charge flow in coulombs (C)
• $I$I = current in amperes (A)
• $t$t = time in seconds (s)

Rearranging: $I = \dfrac{Q}{t}$I=tQ​ and $t = \dfrac{Q}{I}$t=IQ​

Quantity	Symbol	Unit	Unit Symbol
Charge	Q	Coulombs	C
Current	I	Amperes	A
Time	t	Seconds	s