GATE EE 2010 Electrical and Electronic Measurements Solution Q 4 - Grad Plus

# GATE EE 2010 Electrical and Electronic Measurements Solution Q 4

An ammeter has a current range of 0-5 A, and its internal resistance is 0.222. In order to change the range to 0-25 A, we need to add a resistance of __

(a) 0.8 Ω in series with the meter

(b) 1.0 Ω in series with the meter

(c) 0.04 Ω in parallel with the meter

(d) 0.05 Ω in parallel with the meter

Ans. (d)

Explanation

To extend the range of the ammeter, a shunt resistance is connected across the meter.

Im= full scale deflection current = 5A

Full scale current to be measured, I=25 A

Hence, m=\frac{I}{I_{m}}=\frac{25}{5}=5

\frac{I}{I_{m}}=\frac{R_{sh}+R_{m}}{R_{sh}} m=1+\frac{R_{m}}{R_{sh}} R_{sh}=\frac{R_{m}}{m-1}=\frac{0.2}{5-1}=0.05
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