A galvanometer having a resistance of 26.0 ? has a 1.00-? shunt resistance insta

Question

A galvanometer having a resistance of 26.0 ? has a 1.00-? shunt resistance installed to convert it to an ammeter. It is then used to measure the current in a circuit consisting of a 16.0-? resistor connected across the terminals of a 55.0-V battery having no appreciable internal resistance.

(a) What current does the ammeter measure?
A

(b) What should be the true current in the circuit (that is, the current without the ammeter present)?
A

(c) By what percentage is the ammeter reading in error from the true current?
%

Explanation / Answer

(a)
rm = (26*1)/(26 + 1)= 26/27 ?
Ic = 55/(16 + 26/27)
Ic = 3.242 A.....ammeter current

(b)
I = E/R = 55/16
I = 3.4375 A.....actual current

(c)
% = 3.242/3.4375 = 0.9432
% error = (1 - 0.9432) * 100 = 5.66% smaller

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