The galvanometer shown in the circuit has a resistance of 5 Ω. Find the current through the galvanometer using Thevenin’s theorem.

Fig.22(a)

Derive a mathematical expression for the average real power deliver by a single phase a.c. source with an e.m.f of \(e=\sqrt{2}E_m\sin\omega t\) when the source current is \(i=\sqrt{2}I_m\sin\left(\omega t-\theta\right)\). Define power factor of an a.c. circuit. State the major disadvantage of poor power factor.

Derive an expression for the resonant frequency of a parallel circuit, one branch consisting of a coil of inductance L and resistance R and the other branch of capacitance C.

Explain

• Star – delta conversion
• Delta – star conversion with the help of a purely resistive circuit

A circuit receives 50 A current at a power factor of 0.8 lag from a 250, 50 Hz, 1-ph A.C. supply. Calculate the capacitance of the capacitor which is required to be connected across the circuit to make the power factor unity.

Find the current in each branch of the network using Kirchhoff’s law

Fig.23