Alternating Current MCQs for NEET — Physics Questions with Answers

A transformer has an efficiency of 90% is working on 200 V and 3 kW power supply. If the current in the secondary coil is 6 A the voltage across the secondary coil and the current in the primary coil respectively are:

The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux Ï• linked with the primary coil is given by Ï•=${\varphi }_0$+4t, where Ï• is in weber, t is time in second and Ï•₀is a constant, the output voltage across the secondary coil is:

If the current in an AC circuit is given as $\mathrm{i}=\left(5\mathrm{A}\right)\sin \left(\mathrm{\omega t}-\frac{\mathrm{\pi }}{3}\right)$ when an emf $\mathrm{e}=\left(200\mathrm{V}\right)\mathrm{sin\omega t}$ is applied across the circuit. The circuit having component only

A step-down transformer is employed to reduce the main supply of AC from 220V to 11V. If the primary coil draws a current of 5A and the secondary supplies a current of 90A, then the efficiency of the transformer is  -

At resonance, the value of the power factor of the circuit is -

In a LCR circuit having L = 8.0 henry, C = 0.5 $\mathrm{\mu F}$ and R = 100 $\mathrm{\Omega }$ in series, the resonance frequency (in Hz) is 

In a LCR series network, ${\mathrm{V}}_{\mathrm{L}}=40 \mathrm{V}, {\mathrm{V}}_{\mathrm{C}}=20 \mathrm{V} \mathrm{and} {\mathrm{V}}_{\mathrm{R}}=15 \mathrm{V}$. The supply voltage is

The ratio of the number of turns in secondary to primary in an ideal transformer varies from 50 to 550. If the power input is P, then its output power is  -

Loss in energy in the transformer is due to 

$\mathrm{An} \mathrm{alternating} \mathrm{current} \mathrm{is} \mathrm{given} \mathrm{as} \mathrm{i} = {\mathrm{i}}_1 \cos \mathrm{\omega t} - {\mathrm{i}}_2 \sin \mathrm{\omega t}. \mathrm{The} \mathrm{rms} \mathrm{current} \mathrm{is} \mathrm{given} \mathrm{by}$