Question

An LPF wattmeter of power factor 0.2 is having three voltage settings 300 V, 150 V and 75 V, and two current settings 5A and 10 A. The full scale reading is 150. If the wattmeter is used with 150 V voltage setting and 10 A current setting, the multiplying factor of the wattmeter is

• A. 2

Answer 1

The correct option is A 2
Given,

$cos\varphi =0.2\left(LPFwattmeter\right)$

Given, full scale reading of wattmeter,

$W_m=150Watt$

$Also,forV=150volt,I=10Asettings,$

Wattmeter reading,

$W=VIcos\varphi$

$150\times 10\times 0.2=300$

$\therefore$ Multiplying factor of wattmeter,

$m=\frac{W}{W_m}=\frac{300}{150}=2$