21.If 20 V battery is connected to primary coil of a transformer, then output voltage is:

22.If a dry cell of emf 1.5 V is connected across the primary of a step-up transformer of turn ratio 3: 4, then the voltage developed across the secondary is:

23.In a series L-C-R circuit, the voltage across each resistance, inductance and capacitance is 10 V. If the resistance is short-circuited, the current in the circuit will be:

24.The magnetic field between the plates of radius 12 cm separated by distance of 4 mm of a parallel plate capacitor of capacitance 100 pF along the axis of plates having conduction current of 0.15 A is:

25.An AC circuit consists of a resistance and a choke in series. The resistance is of 220? and choke is of 0.7 H. The power absorbed from 220 V and 50 Hz, source connected with the circuit, is: