Electrical Measuring Instruments | Practice MCQs Physics for Mdcat | mosaicbro.com
Electrical Measuring Instruments | Practice MCQs Physics for Mdcat
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Review Answers:
29
A cylindrical bar magnet is kept along the axis of a circular coil. On rotating magnet about its axis, the coil will have induced in it:
Correct Answer:B
Explanation:
Rotating the magnet about its axis does not change the flux through the coil, so no current is induced.
30
When a magnet with its magnetic moment along the axis of a circular coil and directed towards the coil is withdrawn away from the coil, parallel to itself, the current in the coil, as seen by the withdrawing magnet is:
Correct Answer:B
Explanation:
According to Lenz’s law, the induced current will oppose the withdrawal, creating a clockwise current.
31
A coil of insulated wire is connected to a battery. If it is taken to galvanometer, its pointer is deflected, because:
Correct Answer:A
Explanation:
The changing current in the coil induces a current in the galvanometer, causing deflection.
32
When the rate of change of current is unity, the induced e.m.f. is equal to:
Correct Answer:B
Explanation:
The induced e.m.f. is given by $\mathcal{E} = -L \frac{di}{dt}$, so when $\frac{di}{dt} = 1$, $\mathcal{E} = -L$.
33
When current $i$ is passed through an inductor of self inductance $L$, energy stored in it is $\frac{1}{2} L i^2$. This is stored in the:
Correct Answer:C
Explanation:
The energy is stored in the magnetic field created by the inductor.
34
A dynamo:
Correct Answer:B
Explanation:
A dynamo converts mechanical energy (rotation) into electrical energy.
35
A transformer:
Correct Answer:C
Explanation:
A transformer changes the voltage level while keeping the frequency constant.