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Electromagnetic Induction

128 Questions Start Allen Test
All Exams Allen
Q26 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
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 :-
A.
4 sec
B.
2 sec
C.
1 sec
D.
0.5 sec
Q27 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
Which statement is correct from following –
(a) Inductor store energy in the form of magnetic field
(b) Capacitor store energy in the form of electric field
(c) Inductor store energy in the form of electric and magnetic field both
(d) Capacitor store energy in the form of electric and magnetic field both
A.
a, b
B.
a, c
C.
b, d
D.
b, c
Q28 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
If a current of 2A give rise a magnetic flux of $5 \times 10^{-5}$ weber/turn through a coil having 100 turns, then the magnetic energy stored in the medium surrounding by the coil is:
A.
5 joule
B.
$5 \times 10^{-7}$ joule
C.
$5 \times 10^{-3}$ joule
D.
0.5 joule
Q29 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
For a solenoid keeping the turn density constant its length makes halved and its cross section radius is doubled then the inductance of the solenoid increased by :-
A.
200%
B.
100%
C.
800%
D.
700%
Q30 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
A constant current I is maintained in a solenoid. Which of the following quantities will increase if an iron rod is inserted in the solenoid along its axis:-
(a) Magnetic field at the centre
(b) Magnetic flux linked with the solenoid
(c) Self inductance of the solenoid
(d) Rate of Joule heating
A.
a, b, c
B.
c, d
C.
a, b
D.
Only b
Q31 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
The inductance of a solenoid is 5H and its resistance is 5Ω. If it is connected to a 10 volt battery then time taken by the current to reach 9/10 $^{th}$ of its maximum will be :-
A.
4.0 s
B.
2.3 s
C.
1.4 s
D.
1.2 s
Q32 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
An LR circuit with a battery is connected at t = 0. Which of the following quantities is not zero just after the connection :-
(a) Current in circuit
(b) Magnetic potential energy in the inductor
(c) Power delivered by the battery
(d) Emf induced in the inductor
A.
a, b
B.
a, c
C.
c, d
D.
Only d
Q33 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
During 0.1s current in a coil increases from 1A to 1.5A. If inductance of this coil is $60~\mu \mathrm{H}$ , induced current in external resistance of $600~\mu \Omega$ is :-
A.
1A
B.
$4 / 3\mathrm{A}$
C.
$2 / 3\mathrm{A}$
D.
$1 / 2\mathrm{A}$
Q34 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
In the circuit shown in figure what is the value of $I_{1}$ just after pressing the key K?
A.
$\frac {5}{7} \mathrm{A}$
B.
$\frac {5}{1 1} \mathrm{A}$
C.
1A
D.
None of the above
Q35 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
Pure inductors each of inductance 3H are connected as shown. The equivalent induction of the circuit is :-
A.
1H
B.
2H
C.
3H
D.
9H
Q36 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
The time constant of an inductance coil is $2.0 \times 10^{-3} \mathrm{~s}$ . When a $90 \Omega$ resistance is joined in series, the time constant becomes $0.5 \times 10^{-3} \mathrm{~s}$ . The inductance and resistance of the coil are:
A.
$30 \mathrm{mH}; 30 \Omega$
B.
$30 \mathrm{mH}; 60 \Omega$
C.
$60 \mathrm{mH}; 30 \Omega$
D.
$60 \mathrm{mH}; 60 \Omega$
Q37 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
A cylindrical iron core supports N turns. If a current I produces a magnetic flux $\phi$ across the core's cross section, then the magnetic energy is :-
A.
$\mathrm{I}\phi$
B.
$\frac{1}{2}\mathrm{I}\phi$
C.
$\frac{\mathrm{I}^2\phi}{2}$
D.
$\mathrm{I}^2\phi$
Q38 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
The self-inductance of a toroid is (N: no. of turns, r: radius of cross section, $R_{m}$ : mean radius of toroid):
A.
$\frac{\mu_{0}N^{2}r^{2}}{2R_{m}}$
B.
$\frac{\mu_{0}N^{2}\pi r}{2R_{m}}$
C.
$\frac{\mu_{0}N^{2}r}{2R_{m}}$
D.
$\frac{\mu_{0}N^{2}r\pi}{R_{m}}$
Q39 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
An inductance L and a resistance R are joined to a battery. After some time, battery is disconnected but L and R remains connected to the closed circuit. The current strength will be reduced to 37% of its initial value in :
A.
RL sec
B.
R/L sec
C.
L/R sec
D.
1/LR sec
Q40 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
Energy is stored in the choke coil in the form of:
A.
Heat
B.
Electric field
C.
Magnetic field
D.
Electro-magnetic field
Q41 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
When a current changes from 2A to 4A in 0.05 sec. in a coil, induced emf is 8 V. The self inductance of coil is :-
A.
0.1 H
B.
0.2 H
C.
0.4 H
D.
0.8 H
Q42 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
An e.m.f. of 12 V is induced in a given coil when the current in it changes at the rate of 48 A/min. The inductance of the coil is:-
A.
0.5 henry
B.
15 henry
C.
1.5 henry
D.
9.6 henry
Q43 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
Two conducting coils are placed co-axially now a cell is connected in one coil then they will :-
A.
attract to each other
B.
repel to each other
C.
both 1) & 2)
D.
they will not experience any force
Q44 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
A coil of resistance $10\Omega$ and an inductance 5H is connected to a 100V battery. Then energy stored in the coil is:
A.
125 erg
B.
125 J
C.
250 erg
D.
250 J
Q45 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
The energy density in magnetic field B is proportional to:-
A.
$\frac{1}{B}$
B.
$\frac{1}{B^{2}}$
C.
B
D.
$B^{2}$
Q46 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
Inductance of a solenoid is 3H and it consist of 500 turns. If number of turn make twice, then the value of self inductance becomes:-
A.
1.5 H
B.
3 H
C.
9 H
D.
12 H
Q47 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
A coil of 40 henry inductance is connected in series with a resistance of 8 ohm and the combination is joined to the terminals of a 2 volt battery. The time constant of the circuit is:-
A.
$\frac{1}{5}$ sec
B.
40 sec
C.
20 sec
D.
5 sec
Q48 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
When current in a coil is reduced from 2A to 1A in 1ms, the induced emf is 5V. The inductance of coil is:
A.
5 H
B.
5000 H
C.
5 mH
D.
50 H
Q49 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
A coil of inductance 300mH and resistance 2Ω is connected to a source of voltage 2V. The current reaches half of its steady state value in:
A.
0.3 s
B.
0.15 s
C.
0.1 s
D.
0.05 s
Q50 Allen SELF INDUCTION AND L–R DC CIRCUIT MCQ
An ideal coil of 10H is connected in series with a resistance of $5\Omega$ and a battery of 5V. 2 seconds after the connection is made, the current flowing in amperes in the circuit is:
A.
e
B.
e -1
C.
$(1-e^{-1})$
D.
$(1-e)$