In the circuit shown below, what would be the wattmeter reading?a)640 ...
Wattmeter:
A wattmeter is an electrical instrument that is used to measure the electric power of any electrical circuit.
The internal construction of a wattmeter is such that it consists of two coils. One of the coils is in series and the other is connected in parallel.
The coil that is connected in series with the circuit is known as the current coil and the one that is connected in parallel with the circuit is known as the voltage coil
Wattmeter measures the average power.
The reading of wattmeter will be,
Average power = Vpc Icc cos ϕ
Where,
Vpc is the voltage across pressure coil
Icc is current flows through the current coil
ϕ is the phase angle between Vpc and Icc
So, wattmeter is a device capable of detecting voltage, current and the angle between the voltage and the current to provide power readings.
Calculation:
Given,
Vpc = V = 200 ∠0° V
Z = Impedance = 4 +j3 = 5∠36.87°
I
= Current from supply =
Icc = 40 × (5/50) = 4 A
ϕ = 36.87°
From concept
Average power = 200 × 4 × cos 36.87° = 640 W