A galvanometer with full-scale deflection of 10 mA is to ...
A galvanometer with full-scale deflection of 10 mA is to be converted to a voltmeter with full-scale deflection of 5v. if a series resistance of 498Ω is used for the conversion, the resistance of the galvanometer is ?
1Ω
2Ω
5Ω
10Ω
Correct answer is B
r = resistance of the galvanometer
l = current through galvanometer = 1mA or 0.01A
V1 = p.d across the galvanometer = I X r = 0.01 X r
: V1 = 0.01r
V2 = p.d across the multiplier = 5 - 0.01r
R = resistance of the multiplier = 498Ω
where R = VI --> 498 = 5−0.01r0.01
CROSS MULTIPLY --> 498 X 0.01 = 5 - 0.01r
0.01r = 5 - 4.98
∴ r = 0.020.01 = 2Ω