(a) The diagram shows a circuit with two resistors, R and S - Edexcel - GCSE Physics - Question 6 - 2018 - Paper 1

To find the potential difference (V) across resistor R, we can use Ohm's Law, which states that:

$V = I imes R$

Where:

• V is the potential difference (voltage) across the resistor,
• I is the current through the resistor,
• R is the resistance of the resistor.

First, we need to determine the current through resistor R. We know from the circuit that the total current entering the junction is 0.60 A and the current exiting the junction is 0.40 A. Therefore, the current through R is:

$I = 0.60 A - 0.40 A = 0.20 A$

Now, plug the values into Ohm's Law with R = 15 Ω:

$V = 0.20 A imes 15 Ω = 3.0 V$

Thus, the potential difference across R is 3.0 V.