Physics
Physics
Problem
A resistor is connected across a DC supply. When a voltmeter of resistance is connected across the resistor, the total current drawn from the supply increases. Calculate the percentage error introduced in the resistor current because of the voltmeter connection. a) b) c) d)Intuitive explanation
When you connect a voltmeter across a resistor, you're actually adding a parallel path for current—the voltmeter itself draws current because it has finite resistance. The key insight is that the voltmeter and resistor now share the voltage, so the current through the resistor decreases from its ideal value. To find the percentage error, calculate the original current without the voltmeter, then the new current when they're in parallel, and compare how much the resistor's current dropped relative to its ideal value.
Intuitive explanation
When you connect a voltmeter across a resistor, you're actually adding a parallel path for current—the voltmeter itself draws current because it has finite resistance. The key insight is that the voltmeter and resistor now share the voltage, so the current through the resistor decreases from its ideal value. To find the percentage error, calculate the original current without the voltmeter, then the new current when they're in parallel, and compare how much the resistor's current dropped relative to its ideal value.