Lesson: Design of the Voltmeter Physics

In this lesson, we will learn how to describe the combining of a galvanometer with a multiplier resistor to design a DC voltmeter.

Lesson Plan

Students will be able to

describe the appropriate connection of a galvanometer and multiplier resistor to produce a voltmeter,
explain the required resistance ratio of the galvanometer and multiplier,
calculate the measurement range of a voltmeter from the current required for a full-scale deflection of the galvanometer and the ratio of the resistance of the galvanometer to the multiplier.

Lesson Presentation

Lesson Video

Lesson Explainer

Lesson Worksheet

Q1:

A voltmeter is used to measure the voltage of a direct-current source that is estimated to have a voltage of several volts. The galvanometer in the voltmeter has a resistance of a few milliohms. Which of the following correctly explains why the multiplier resistor in such a voltmeter must have a resistance much greater than the resistance of the galvanometer that the multiplier is connected in series with?

Q2:

Which of the following is the most correct description of how the range of values of voltages that a galvanometer being used as a voltmeter can produce can be extended when a multiplier resistor is used?

Q3:

The voltage in the circuit shown is 12 V, which is the greatest voltage that can be measured using the circuit as a voltmeter. The resistance of the galvanometer is one-hundredth of the resistance of the multiplier.

Find , the voltage across the galvanometer. Answer to the nearest millivolt.

Find , the voltage across the multiplier. Answer to one decimal place.