A voltmeter of resistance 400 is utilized to measure the potential difference across a 100 resistor in a circuit consisting of an 84 V battery connected in series with the 100 resistor and a 200 resistor. Calculate the potential difference across the 100 resistor before the voltmeter is connected.

Step-by-step solution

Before the voltmeter is connected, the circuit consists of the 100 and 200 resistors in series with the 84 V battery. Total resistance of the circuit is: R_ eq = 100 + 200 = 300 Current flowing through the circuit is: I = V R_ eq = 84 300 A The potential difference across the 100 resistor is: V₁₀₀ = I 100 = 84 300 100 = 28 V