## Electromagnetic Induction Quiz-3

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background.

Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced.

Q21. A circular coil of mean radius of 7 cm and having 400 turns is rotated at the rate of 1800 revolutions per minute in the earth’s magnetic field (B=0.5 gauss), the maximum e.m.f. induced in coil will be
•  1.158 V
•  0.58 V
•  0.29 V
•  5.8 V
Solution

Q22.Consider the statements:
(I)If magnetic field, B =0, then magnetic flux is also zero.
(II)If magnetic flux, Ï•=0,then magnetic field is also zero.
•  (I)is true , (II) may be true
•  Both (I) and (II) are true
•  (I) may be true, (II) is true
•  (I) and (II) both are false
Solution

Q23.  A circular coil and a bar magnet placed near by are made to move in the same direction. The coil covers a distance of 1 m in 0.5 sec and the magnet a distance of 2m in 1 sec. The induced emf produced in the coil
•   Zero
•  1 V
•  0.5 V
•  Cannot be determined from the given information
Solution

Q24. A cylindrical bar magnet is kept along the axis of a circular coil. If the magnet is rotated about its axis, then
•  A current will be induced in a coil
•  No current will be induced in a coil
•  Only an e.m.f. will be induced in the coil
•  An e.m.f and a current both will be induced in the coil
Solution
Because there is no change in flux linked with coil

Q25.When power is drawn from the secondary coil of the transformer, the dynamic resistance
•  Increases
•  Decreases
•  Remains unchanged
•  Changes erratically
Solution
When the secondary coil circuit is open, the magnetic flux in the core is produced by the primary current only. When the secondary circuit is closed, the currents in the secondary coil also produce magnetic flux in the core but in opposite direction. This decreases the core flux and hence reduces the back emf more current is drawn in the primary coil. Hence, power factor is no longer zero. The power factor has increased or the phase difference is no longer 90°,i.e., phase difference has decreased. Thus, dynamic resistance has increased

Q26. The mutual inductance of an induction coil is 5H. In the primary coil, the current reduces from 5A to zero in 10-3 s. What is the induced emf in the secondary coil
•  2500V
•  25000V
• 2510V
•  Zero
Solution

Q27.An alternating current of frequency 200 rad/sec peak value 1A as shown in the figure, is applied to the primary of a transformer. If the coefficient of mutual induction between the primary and the secondary is 1.5H, the voltage induced in the secondary will be

•  300 V
•  191 V
•  220 V
•  471 V
Solution

Q28.An L-R circuit has a cell of e.m.f. E, which is switched on at time t=0. The current in the circuit after a long time will be
•  Zero
•  E/R
•  E/L
•  E/√(L2+R2 )
Solution
E/R

Q29.Current in a coil changes from 5 A to 10 A in 0.2 s. If the coefficient of self-induction is 10 H, then the induced emf is
•  112 V
•  250 V
•  125 V
•  230 V
Solution

Q30. Choke coil works on the principle of
•  Transient current
•  Self induction
•  Mutual induction
• Wattless current
Solution
Self induction

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