Electrical Measuring Instruments | Practice MCQs Physics for Mdcat | mosaicbro.com

Electrical Measuring Instruments | Practice MCQs Physics for Mdcat

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22 Post office box is an arrangement for finding resistance of a conductor and it makes use of:
Correct Answer: A
Explanation: The post office box operates on the Wheatstone bridge principle.
23 A galvanometer of resistance 25 Ohm and having full scale deflection for a current of 10 mA is changed into voltmeter of range 100 volts by connecting a resistor R in series with the galvanometer.
Correct Answer: D
Explanation: The required series resistance $R$ is calculated as $R = \frac{V}{I_g} - G = \frac{100}{0.01} - 25 = 9975 \, \Omega$.
24 A voltmeter with a resistance of $50 \times 10^3$ Ohm is used to measure voltage in a circuit. To increase its range to 3 times, the additional resistance to be put in series is:
Correct Answer: A
Explanation: The additional resistance required is $R_{add} = (n-1)R_v = (3-1) \times 50 \times 10^3 = 10^6 \, \Omega$.
25 An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of:
Correct Answer: C
Explanation: The induced e.m.f. depends on the rate of change of flux, not the resistivity of the wire.
26 A magnet is moved towards a coil (I) quickly (II) slowly, then the induced e.m.f. is:
Correct Answer: A
Explanation: A faster movement induces a larger e.m.f. due to a higher rate of change of flux.
27 Lenz’s law is consequence of the law of conservation of:
Correct Answer: C
Explanation: Lenz’s law ensures that the induced current opposes the change in flux, conserving energy.
28 The law of electromagnetic induction have been used in the construction of a:
Correct Answer: D
Explanation: Generators operate on the principle of electromagnetic induction.
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