A 300 V, 5A, 0.2 pf low power factor wattmeter is used to measure the power consumed by a load

Q. A 300 V, 5A, 0.2 pf low power factor wattmeter is used to measure the power consumed by a load. The wattmeter scale has 150 divisions and the pointer is on the 100^th division. The power consumed by the load (in Watts) is .

Ans: 200

Sol:

Given that, voltage (V) = 300 V current (I) = 5A power factor (cos ϕ) = 0.2 Full scale reading of wattmeter, P = VI cos ϕ = 300 × 5 × 0.2 = 300 W Wattmeter scale has 150 divisions.

Each division constitutes,

of reading.

While measuring the power consumed by a load, pointer is on the 100th division, 100 divisions constitute 100 × 2 = 200 W of power.