Question

In the given dc circuit, a voltmeter whose resistance is 6000 ohm is used to measure the voltage drop across the 3000 ohm resistor. Determine the % difference in the voltmeter reading that is observed when compared to the true voltage across 3000 ohm resistor when the voltmeter is not connected.

Answer 1

The true voltage drop across the three resistors in series is divided in proportion their resistances.

Voltage across 3000 ohm resistor V,

When the voltmeter of resistance 6000 ohm is connected across 3000 ohm, the effective resistance of the 3000 ohm arm will be,

So the voltmeter reading will be:

Percentage error

Voltmeter reading will be 16.6 % lesser than the true voltage across 3000 ohm resistor.