DC Power Measurement

Q. A dc A-h meter is rated for 15 A, 250 V. The meter constant is 14.4 A-sec/rev. The meter constant at rated voltage may be expressed as

1. 3750 rev/kWh
2. 3600 rev/kWh
3. 1000 rev/kWh
4. 960 rev/kWh

Q. For the circuit in the figure, the voltage and current expressions are:
$v\left(t\right)=E_{1}sin\left(\omega t\right)+E_{3}sin\left(3\omega t\right)$
and $i\left(t\right)=I_{1}sin(\omega t-{\varphi }_1)+I_{3}sin(3\omega t-{\varphi }_3)+I_{5}sin\left(5\omega t\right)$
The average power measured by the Wattmeter is

1. $\frac{1}{2}{E}_1{I}_{1}cos{\varphi }_1$
2. $\frac{1}{2}[E_1{I}_{1}cos{\varphi }_1+E_1{I}_{3}cos{\varphi }_3+E_1{I}_5]$
3. $\frac{1}{2}[E_1{I}_{1}cos{\varphi }_1+E_3{I}_{3}cos{\varphi }_3]$
4. $\frac{1}{2}[E_1{I}_{1}cos{\varphi }_1+E_3{I}_{1}cos{\varphi }_1]$