An LPF wattmeter of power factor 0.2 is having three voltage

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

1. 1
2. 2
3. 3
4. 4

Correct Option: B

In LPF wattmeter, T_d on the moving system is small owing to low power factor even when the current and potential coils are fully excited. Also the error sint roduced due to inductance of pressure coil tend to be large at low power factors. So for calculating multiplying factor for a low p.f. wattmeter, p.f. mentioned on the wattmeter should be taken into account.
Therefore,
Multiplying Factor = (Current range used *Voltage range used*p.f)/Power at FSD
Given, Power at Full scale reading = 150
Current Range used = 10 A
Voltage Range used = 150 V
Power Factor = 0.2

Therefore, m =	10 × 150 × 0.2	= 2
	150