A galvanometer has an internal resistance of 27 and deflects full scale for a 50

ID: 1581578 • Letter: A

Question

A galvanometer has an internal resistance of 27 and deflects full scale for a 50-A current.

1) Describe how to use this galvanometer to make an ammeter to read currents up to 40 A .

2) What is the value of this resistor?

3) Describe how to use this galvanometer to make a voltmeter to give a full-scale deflection of 200 V .

4) What is the value of this resistor?

For part 1) I already got the correct answer which was a), but I could not figure out how to do the other ones.

a) A resistor must be placed in parallel with the galvanometer. b) A resistor must be placed in series with the galvanometer.

1) a) A resistor must be placed in parallel with the galvanometer

2) Ia * R = Is * R'

R = (50 * 10-6 * 27) / (40)

R = 33.75 mu.ohms

3) a) A resistor must be placed in series with the galvanometer.

4) R = V / I = 200 / (50 * 10-6)

R = 4.00 M.ohm

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