A 1000 Ω resistor is in a circuit with 30.0 mA flowing through it. A voltmeter with internal resistance 1000 Ω is used to measure the voltage across the resistor. What is the reading on the voltmeter if a total current of 30.0 mA still flows in the circuit?
A) 30.0 V
B) 29.9 V
C) 27.0 V
D) 15.0 V
E) 3.00 V

Question

Quizplus · Accepted Answer

First, we can use Ohm's Law to find the voltage across the resistor:
V = IR = (0.030 A)(1000 Ω) = 30 V

However, we need to take into account the internal resistance of the voltmeter, which will affect the voltage reading.

Using a voltage divider formula, we can find the actual voltage measured by the voltmeter:
V_actual = V_measured * (R_volmeter / (R_resistor + R_volmeter))
where R_resistor is the resistance of the resistor (1000 Ω) and R_volmeter is the internal resistance of the voltmeter (1000 Ω).

Plugging in the values, we get:
V_actual = 30V * (1000Ω / (1000Ω + 1000Ω)) = 15V

Therefore, the reading on the voltmeter will be 15V, which corresponds to choice D.

A 1000 Ω Resistor Is in a Circuit with 30