Question

A wattmeter is connected as shown in below figure. Wattmeter has a current coil of $0.1\Omega$ resistance. Percentage of error in reading of wattmeter when it is connected to a load of 12 A at 250 V with unity power factor is

• A. 0.52%
• B. 0.48%
• C. 0.32%
• D. 0.64%

Answer 1

The correct option is B 0.48%

$Percentageerror=\frac{I^2{R}_C}{VIcos\varphi }$

$=\frac{(12{)}^2\times 0.1}{250\times 12\times 1}\times 100$

$=\frac{14.4}{3000}\times 100=0.48\%$