Resistance and Ohm's Law

This lesson covers resistance, Ohm's law and the factors affecting resistance, as required by AQA GCSE Combined Science Trilogy (8464, section 6.2.1). Understanding resistance and how it relates to current and potential difference is essential for circuit calculations.

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What Is Resistance?

Resistance is a measure of how difficult it is for current to flow through a component. The greater the resistance, the smaller the current for a given potential difference.

Resistance is measured in ohms (Ω).

The Resistance Equation

$V = I \times R$V=I×R

Where:

• $V$V = potential difference in volts (V)
• $I$I = current in amperes (A)
• $R$R = resistance in ohms (Ω)

Rearranging: $R = \dfrac{V}{I}$R=IV​ and $I = \dfrac{V}{R}$I=RV​

Quantity	Symbol	Unit	Unit Symbol
Potential difference	V	Volts	V
Current	I	Amperes	A
Resistance	R	Ohms	Ω

Exam Tip (AQA 8464): You must be able to rearrange $V = IR$V=IR confidently. Cover the quantity you want in the formula triangle: V at the top, I and R at the bottom.

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