Electromagnetic Induction - Live Session - NEET 2020Contact Number: 9667591930 / 8527521718

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1.

A coil having an area of 2 m^{2} is placed in a magnetic field which changes from 1 Weber/m^{2} to 4 Weber/m^{2} in 2 seconds. The e.m.f. induced in the coil will be :–

1. 4 volt

2. 3 volt

3. 2 volt

4. 1 volt

2.

A flexible wire bent in the form of a circle is placed in a uniform magnetic field perpendicular to the plane of the coil. The radius of the coil changes as shown figure. The induced emf in the coil is :-

1. 2.

3. 4.

3.

A square loop of side 22 cm is changed to a circle in time 0.4 s. The magnetic field present is 0.2 T. The emf induced is :-

1. –6.6 mV

2. –13.2 mV

3. +6.6 mV

4. +13.2 mV

4.

Which one of the following can produce maximum induced emf :-

1. 50 ampere dc

2. 50 ampere 50 Hz ac

3. 50 ampere 500 Hz ac

4. 100 ampere dc

5.

A solenoid of 10 henry inductance and 2 ohm resistance, is connected to a 10 volt battery. In how much time the magnetic energy will be increased to 1/4 th of the maximum value?

1. 3.5 sec

2. 2.5 sec

3. 5.5 sec

4. 7.5 sec

6.

An inductance coil have the time constant 4 sec, if it is cut into two equal parts and connected parallel then new time constant of the circuit :-

1. 4 sec

2. 2 sec

3. 1 sec

4. 0.5 sec

7.

Which statement is correct from following –

(i) Inductor store energy in the form of magnetic field

(ii) Capacitor store energy in the form of electric field

(iii) Inductor store energy in the form of electric and magnetic field both

(iv) Capacitor store energy in the form of electric and magnetic field both

1. i, ii

2. i, iii

3. ii, iv

4. ii, iii

8.

For a solenoid keeping the turn density constant its lenght makes halved and its cross section radius is doubled then the inductance of the solenoid increased by:–

1. 200%

2. 100%

3. 800%

4. 700%

9.

In the circuit shown in figure bulb will become suddenly bright if:-

1. Key is closed

2. Key is opened

3. Key is opened or closed

4. Would not become bright

10.

A conducting rod of 1m length rotating with a frequency of 50 rev/sec. about its one of end inside the uniform magnetic field of 6.28 mT. The value of induced emf between end of rod is :-

1. 1 V

2. 2 V

3. 0.5 V

4. 0.25 V

11.

A semicircle loop PQ of radius 'R' is moved with velocity 'v' in transverse magnetic field as shown in figure. The value of induced emf. between the ends of loop is :-

1. Bv ($\mathrm{\pi}$ r), end 'P' at high potential

2. 2 BRv, end P at high potential

3. 2 BRv, end Q at high potential

4. B$\frac{{\mathrm{\pi R}}^{2}}{2}\mathrm{v}$, end P at high potential

12.

Two long parallel metallic wires with a resistance 'R' form a horizontal plane. A conducting rod AB is on the wires shown in figure. The space has magnetic field pointing vertically downwards. The rod is given an initial velocity 'v_{0}'. There is no friction in the wires and the rod. After a time 't' the velocity v of the rod will be such that:–

1. v > v_{0}

2. v < v_{0}

3. v = v_{0}

4. v = –v_{0}

13.

If a bar magnet is dropped vertically into a, long copper tube then its final acceleration will be:-

1. a = g

2. a > g

3. a < g

4. a = 0

14.

A coil of mean area 500 cm^{2 }and having 1000 turns is held perpendicular to a uniform field of 0.4 gauss. The coil is turned through 180$\xb0$ in $\frac{1}{10}$ second. The average induced e.m.f. :–

1. 0.04 V

2. 0.4 V

3. 4 V

4. 0.004 V

15.

An emf induced in a coil, the linking magnetic flux

1. Must decrease

2. Must increase

3. Must remain constant

4. Can either increase of decrease

16.

The magnetic flux through a circuit of resistance R changes by an amount $\u25b3\mathrm{\varphi}$ in time interval $\u25b3$t, then the total amount of charge that passes through the circuit is

1. $\frac{\u25b3\mathrm{\varphi}}{\u25b3\mathrm{t}}$

2. $\frac{\u25b3\mathrm{\varphi}}{\mathrm{R}}$

3. $\frac{\u25b3\mathrm{\varphi}}{\mathrm{R}\u25b3\mathrm{t}}$

4. $\mathrm{R}\u25b3\mathrm{t}$

17.

The magnetic flux linked with a coil at any instant t (in seconds) is given by $\mathrm{\varphi}$ (in Wb) = 8t^{2} – 16t + 500. The induced emf in the coil at t=2s is

1. 516 V

2. 16 V

3. 32 V

4. Zero

18.

A rectangular loop is in uniform magnetic field such that its plane is perpendicular to the magnetic field as shown in the figure. If the loop is pulled out of the field, then the direction of induced current is

1. Clockwise

2. Anti-clockwise

3. Maybe clockwise or anti-clockwise depends on its velocity

4. No current will induce

19.

Two coils each of inductance L are mutually coupled perfectly such that magnetic flux of one coil opposes the flux of other. If the two coils are connected in series then the effective inductance of the combination is

1. L

2. 2L

3. 4L

4. Zero

20.

In the circuit shown in the figure the switch is closed at t = 0. The current supplied by the battery at this instant is

1.

2. $\frac{\mathrm{\epsilon}}{{\mathrm{R}}_{1}+{\mathrm{R}}_{2}}$

3. $\frac{\mathrm{\epsilon}}{{\mathrm{R}}_{1}+{\mathrm{R}}_{3}}$

4. $\frac{\mathrm{\epsilon}\left({\mathrm{R}}_{2}+{\mathrm{R}}_{3}\right)}{{\mathrm{R}}_{1}\left({\mathrm{R}}_{2}+{\mathrm{R}}_{3}\right)+{\mathrm{R}}_{2}{\mathrm{R}}_{3}}$

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