Obtain an expresion for average power dissipated in a purely resistive `A.C.` circuit. Define power factor of the circuit and state its value for purely resistive `A.C.` circuit.
A rectangular coil of a moving coil galvanometer contains `50` turns each having area `12cm^(2)`. It is suspended in radial magnetic field `0.025 Wb//m^(2)` by a fibre of twist constant `15xx10^(-10)N-m//degree`. Calculate the sensitivity of the moving coil galvanometer.

Explanation

### Step-by-Step Solution

#### Part A: Average Power Dissipated in a Purely Resistive AC Circuit

1. **Understanding Power in AC Circuits**:
The instantaneous power \( P(t) \) in an AC circuit can be expressed as:
\[
P(t) = V(t) \cdot I(t)
...