A uniform magnetic field is restricted within a region of radius r. The magnetic field changes with time at a rate d B d t . Loop 2 of radius R is outside the region of magnetic field as shown in the figure. Then the emf generated is-

- d B d t πr 2 in l o o p 1 a n d z e r o in loop 2

zero in loop 1 and zero in loop 2

- d B d t πr 2 in loop 1 and - dB dt πr 2 in loop 2

2 d B d t πr 2 in l o o p 1 a n d z e r o in loop 2

A rectangular, a square, a circular and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity, v → = v i ^ . The magnetic field is directed along the negative z-axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

the circular and the elliptical loops

the rectangular, circular and elliptical loops

Physics - Electromagnetic Induction - Quiz-3

A loop abcd is moved across the pole pieces of a magnet as shown in fig. with a constant speed v. When the edge ab of the loop enters the pole pieces at time t = 0 sec. , which one of the following graphs represents correctly the induced emf in the coil?

Some magnetic flux is changed from a coil of resistance 10 ohm. As a result an induced current is developed in it, which varies with time as shown in figure. The magnitude of change in flux through the coil in webers is

0%

2
0%

4
0%

6
0%

None of these

The graph gives the magnitude B(t) of a uniform magnetic field that exists throughout a conducting loop, perpendicular to the plane of the loop. Rank the five regions of the graph according to the magnitude of the emf induced in the loop, greatest first

0%

b > (d = e) < (a = c)
0%

b > (d = e) > (a = c)
0%

b < d < e < c < a
0%

b > (a = c) > (d = e)

Figure (i) shows a conducting loop being pulled out of a magnetic field with a speed v. Which of the four plots shown in figure (ii) may represent the power delivered by the pulling agent as a function of the speed v

0%

a
0%

b
0%

c
0%

d

A rectangular loop is being pulled at a constant speed v, through a region of certain thickness d, in which a uniform magnetic field B is set up. The graph between position x of the right-hand edge of the loop and the induced emf E will be-

The current i in an induction coil varies with time t according to the graph shown in figure. Which of the following graphs shows the induced emf (e) in the coil with time

The inductance of a closed-packed coil of 400 turns is 8 mH. A current of 5 mA is passed through it. The magnetic flux through each turn of the coil is approximately-

0%

$0.1 μ_{0} Wb$
0%

$0.2 μ_{0} Wb$
0%

$1.0 μ_{0} Wb$
0%

$2.0 μ_{0} Wb$

Switch S of the circuit shown in the figure is closed at t = 0. If e denotes the induced emf in L and i, the current flowing through the circuit at time t, which of the following graphs is correct?

A square loop of side 5 cm enters a magnetic field with 1 cms^-1. The front edge enters the magnetic field at t = 0 then which graph best depicts emf

If induction of magnetic field at a point is B and energy density is U, then which of the following graphs is correct?

A long solenoid of diameter 0.1m has 2 $\times 10^{4}$ turns per meter. At the centre of the solenoid, a coil of 100 turns and radius 0.01m is placed with its axis coinciding with the solenoid's axis. The current in the solenoid reduces at a constant rate to 0 A from 4A in 0.05s. If the resistance of the coil is $10 π^{2} Ω$ , the total charge flowing through the coil during this time is

0%

32 $πμC$
0%

16 $μ C$
0%

32 $μ C$
0%

16 $πμC$

A uniform magnetic field is restricted within a region of radius r. The magnetic field changes with time at a rate $\frac{d B}{d t}$ . Loop 2 of radius R is outside the region of magnetic field as shown in the figure. Then the emf generated is-

0%

zero in loop 1 and zero in loop 2
0%

$- \frac{d B}{d t} {πr}^{2} in loop 1 and - \frac{dB}{dt} {πr}^{2} in loop 2$
0%

$- \frac{d B}{d t} {πr}^{2} in l o o p 1 a n d z e r o in loop 2$
0%

$\frac{2 d B}{d t} {πr}^{2} in l o o p 1 a n d z e r o in loop 2$

An electron moves on a straight-line path XY as shown. The abcd is a coil adjacent to the path of the electron. What will be the direction of the current, if any induced in the coil?

0%
abcd
0%
adcb
0%
The current will reverse its direction as the electron goes past the coil.
0%
No current is induced.

A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced emf is

0%

once per revolution
0%

twice per revolution
0%

four times per revolution
0%

six times per revolution

A coil of resistance 400 $Ω$ is placed in a magnetic field. If the magnetic flux $ϕ (W b)$ linked with the coil varies with time t (sec) as $ϕ = 50 t^{2} + 4 .$

The current in the coil at t=2s is

0%

0.5A
0%

0.1A
0%

2A
0%

1A

A rectangular, a square, a circular and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity, $\vec{v} = v \hat{i} .$ The magnetic field is directed along the negative z-axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

0%

the rectangular, circular and elliptical loops
0%

the circular and the elliptical loops
0%

only the elliptical loop
0%

any of the four loops

a long solenoid has 500 turns. When a current of 2 A is passed through it, the resulting magnetic flux linked with each turn of the solenoid is $4 \times 10^{- 3}$ Wh. The self-inductance of the solenoid is

0%

() 2.5 h
0%

() 2.0 H
0%

() 1.0 H
0%

() 4.0 H

A circular disc of radius 0.2 m is placed in a uniform magnetic field of induction $\frac{1}{π}$ $(\frac{W b}{m^{2}})$ in such a way that its axis makes an angle of $60^{°}$ with $\vec{B}$ . The magnetic flux linked with the disc is

0%
0.02 Wb
0%
0.06 Wb
0%
0.08 Wb
0%
0.01 Wb

The current in an L – R circuit builds up to $(3 / 4)^{t h}$ of its steady state value in 4 seconds. The time constant of this circuit is

0%

$\frac{1}{I n 2} s e c$
0%
$\frac{2}{I n 2} s e c$
0%

$\frac{3}{I n 2} s e c$
0%
$\frac{4}{I n 2} s e c$

An emf of 15 volt is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of the currents at time t = $\infty$ and at t = 1 second is-

0%

$\frac{e^{1 / 2}}{e^{1 / 2} - 1}$
0%
$\frac{e^{2}}{e^{2} - 1}$
0%

$1 - e^{- 1}$
0%
$e^{- 1}$

A uniform magnetic field of induction $B$ is confined to a cylindrical region of radius $R$ . The magnetic field is increasing at a constant rate of $\frac{dB}{dt}$ (tesla/second). An electron of charge $q$ , placed at the point $P$ on the periphery of the field experiences an acceleration of:

0%

$\frac{B}{(\sqrt{2} + 1) r}$ towards left.
0%

$\frac{1}{2} \frac{eR}{m} \frac{dB}{dt}$ towards right.
0%

$\frac{eR}{2 m} \frac{dB}{dt}$ towards left.
0%

zero.

A 50 turns circular coil has a radius of 3 cms, it is kept in a magnetic field acting normal to the area of the coil. The magnetic field B increased from 0.10 tesla to 0.35 tesla in 2 milliseconds. The average induced emf in the coil is-

0%

1.77 volts
0%

17.7 volts
0%

177 volts
0%

0.177 volts

A semicircular wire of radius R is rotated with constant angular velocity $ω$ about an axis passing through one end and perpendicular to the plane of the wire.

There is a uniform magnetic field of strength B. The induced emf between the ends is -

0%

${BωR}^{2} / 2$
0%

$2 {BωR}^{2}$
0%

is variable
0%

none of these

In the figure shown a square loop $PQRS$ of side $‘ a ’$ and resistance $‘ r ’$ is placed near an infinitely long wire carrying a constant current $I$ . The sides $PQ$ and $RS$ are parallel to the wire. The wire and the loop are in the same plane. The loop is rotated by $180 °$ about an axis parallel to the long wire and passing through the midpoints of the side $QR$ and $PS$ . The total amount of charge which passes through any point of the loop during rotation is –

0%

$\frac{μ_{0} Ia}{2 πr} \ln 2$
0%

$\frac{μ_{0} Ia}{πr} \ln 2$
0%

$\frac{μ_{0} {Ia}^{2}}{2 πr}$
0%

cannot be found because the time of rotation not given.

A short-circuited coil is placed in a time-varying magnetic field. Electrical power is dissipated due to the current induced in the coil. If the number of turns were to be quadrupled and the wire radius halved, the electrical power dissipated would be –

0%

halved
0%

the same
0%

doubled
0%

quadrupled

A coil having number of turns N and cross-sectional area A is rotated in a uniform magnetic field B with an angular velocity $ω$ . The maximum value of the emf induced in it is –

0%

$\frac{NBA}{ω}$
0%

$NBAω$
0%

$\frac{NBA}{ω^{2}}$
0%

${NBAω}^{2}$

A metal rod moves at a constant velocity in a direction perpendicular to its length. A constant, uniform magnetic field exists in space in a direction perpendicular to the rod as well as its velocity. Select the correct statement (s) from the following :

0%

The entire rod is at the same electric potential
0%

There is an electric field in the rod
0%

The electric potential is highest at the center of the rod and decreases towards its ends
0%

The electric potential is lowest at the center of the rod and increases towards its ends.

The mutual inductance of a pair of coils is 2H. If the current of the coil changes from 10A to zero in 0.1s, the emf induced in the other coil is –

0%

2 V
0%

20 V
0%

0.2 V
0%

200 V

A current-carrying wire is placed below a coil in its plane, with current flowing as shown.

If the current increases –

0%

no current will be induced in the coil
0%

an anticlockwise current will be induced in the coil
0%

a clockwise current will be induced in the coil
0%

the current induced in the coil will be first anticlockwise and then clockwise

The back emf induced in a coil, when current changes from 1 ampere to zero in one milli-second, is 4 volts, the self-inductance of the coil is:

0%

$1 H enry$
0%

$4 H enry$
0%

$10^{- 3} H enry$
0%

$4 \times 10^{- 3} H enry$

0:0:1

Practice Physics Quiz Questions and Answers

0:0:1

Practice Physics Quiz Questions and Answers

Support mcqexams.com by disabling your adblocker.