A Level Physics Practice Exam

In a series circuit, what is the same everywhere in the circuit?

1. Voltage

2. Resistance

3. Current

4. Power

The correct answer is: Current

In a series circuit, the current is the same throughout the entire circuit. This is because there is only one path for the electrons to flow, meaning that the same amount of charge flows through each component connected in the series at any point in time. As the current is constant, each component will draw a different amount of voltage depending on its resistance, following Ohm's Law (V = IR). This means the voltage is not the same everywhere, as it can vary across different components. Resistance in a series circuit adds up, resulting in a total resistance that is the sum of the individual resistances, so it is not uniform across the circuit. Similarly, while power can be calculated for each component using the formula P = I^2R, the total power in the circuit depends on the voltage and current, making it variable as well. For these reasons, the current is the only quantity that remains the same throughout the circuit.