A fighter plane of length 20 m, wing span (distance from tip of one wing to the tip of the other wing) of 15 m and height 5 m is flying towards east over Delhi. Its speed is 240 m s - 1 . The earth's magnetic field over Delhi is 5 × 10 - 5 T with the declination angle ~ 0 o and dip of θ such that sin ⁡ θ = 2 3 . If the voltage developed is V B between the lower and upper side of the plane and V W between the tips of the wings then V B a n d V W are close to :

V B = 45 m V ; V W = 120 m V with left side of pilot at higher voltage

V B = 40 m V ; V W = 135 m V with left side of pilot at higher voltage

V B = 45 m V ; V W = 120 m V with right side of pilot at higher voltage

V B = 40 m V ; V W = 135 m V with right side of pilot at high voltage

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The negative sign in Lenz's law indicates that the flow of current support the change in flux.

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Important Questions on Electromagnetic Induction

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Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

Two straight conducting rails form a right angle as shown below. A conducting bar in contact with the rails starts at the vertex at time

t = 0

and moves with constant velocity of

v = 5 m s^{- 1}

along them. A magnetic field with

B = 0.1 T

is directed out of the page. The absolute value of the

emf

around the triangle at the time

t = 4 s

will be?

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A rigid wire loop of square shape having side of length

L

and resistance

R

is moving along the x-axis with a constant velocity

v_{0}

in the plane of the paper. At

t = 0

, the right edge of the loop enters a region of length

3 L

where there is a uniform magnetic field

B_{0}

into the plane of the paper, as shown in the figure. For sufficiently large

v_{0},

the loop eventually crosses the region. Let

x

be the location of the right edge of the loop. Let

v (x)

I (x)

and

F (x)

represent the velocity of the loop, current in the loop, and force on the loop, respectively, as a function of

x

. Counter-clockwise current is taken as positive.

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Which of the following schematic plot(s) is(are) correct ? (Ignore gravity)

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A rod of length $2 m$ slides with a speed of $5 m s^{- 1}$ on a rectangular conducting frame as shown in figure. There exists a uniform magnetic field of $0.04 T$ perpendicular to the plane of the figure. If the resistance of the rod is $3 Ω$ . The current through the rod is

Question Image

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

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

Question Image

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

10 m

long horizontal wire extends from North East to South West. It is falling with a speed of

5.0 m s^{- 1},

at right angles to the horizontal component of the earth's magnetic field of

0.3 \times 10^{- 4} Wb m^{- 2} .

The value of the induced emf in the wire is:

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A copper ring having a cut such that it does not form a complete loop is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. Then acceleration of the falling magnet is

Question Image

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A metal ring is held horizontally and bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

What does the negative sign indicate in Lenz’s law?

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Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A thin strip $10 c m$ long is on a $U$ shaped wire of negligible resistance and it is connected to a spring of spring constant $0.5 N m^{- 1}$ (see figure). The assembly is kept in a uniform magnetic field of $0.1 T .$ If the strip is pulled from its equilibrium position and released, the number of oscillations it performs before its amplitude decreases by a factor of $e$ is $N$ . If the mass of the strip is $50$ grams, its resistance $10 Ω$ and air drag negligible, $N$ will be close to:
Question Image

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

The figure shows a square loop

L

of side

5 c m

which is connected to a network of resistances. The whole setup is moving towards the right with a constant speed of

1 c m s^{- 1}

. At some instant, a part of

L

is in a uniform magnetic field of

1 T

perpendicular to the plane of the loop. If the resistance of

L

1.7 Ω,

the current in the loop at that instant will be close to:
Question Image

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

Lenz's law provides a relation between

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

Consider a thin metallic sheet perpendicular to the plane of the paper moving with speed

v

in a uniform magnetic field

B

going into the plane of the paper (see figure). If charge densities

σ_{1}

and

σ_{2}

are induced on the left and right surfaces respectively of the sheet, then (ignore fringe effects)

Question Image

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A bicycle generator creates

1.5 V

15 km h^{- 1}

. The EMF generated at

10 km h^{- 1}

is:

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A $1 m$ long thin metal bar of negligible resistance weighing $1 kg$ rests on two metal supports as shown in the figure. The supports are connected in series to an ideal cell and a resistance. A uniform magnetic field $0.5 T$ is applied in the region normal to the plane of the paper and into the paper. Maximum emf that the cell can have without breaking the circuit in volt is
(Acceleration due to gravity $= 10 m s^{- 2}$ )

Question Image

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

If a coil of metal wire is kept stationary in a uniform magnetic field, then_______.

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence, the rod gains gravitational potential energy. The work required to do this comes from

MEDIUM

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

Prove theoretically, the relation between e.m.f induced in a coil and rate of change of magnetic flux in electromagnetic induction.

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

An infinitely long straight wire carrying current $I$ , one side opened rectangular loop and a conductor $C$ with a sliding connector are located in the same plane, as shown in the figure. The connector has length $l$ and resistance $R$ . It slides to the right with a velocity $v$ . The resistance of the conductor and the self-inductance of the loop are negligible. The induced current in the loop, as a function of separation $r$ , between the connector and the straight wire is:

Question Image

HARD

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A fighter plane of length 20 m, wing span (distance from tip of one wing to the tip of the other wing) of 15 m and height 5 m is flying towards east over Delhi. Its speed is

240 m s^{- 1} .

The earth's magnetic field over Delhi is

5 \times 10^{- 5} T

with the declination angle

~ 0^{o}

and dip of

θ

such that

\sin θ = \frac{2}{3} .

If the voltage developed is

V_{B}

between the lower and upper side of the plane and

V_{W}

between the tips of the wings then

V_{B} a n d V_{W}

are close to :

EASY

Physics>Electricity and Magnetism>Electromagnetic Induction>Lenz's Laws and Conservation of Energy

A solid metal cube of edge length

2 cm

is moving in the positive

y

-direction, at a constant speed of

6 m s^{- 1}

. There is a uniform magnetic field of

0 .1 T

in the positive

z

-direction. The potential difference between the two faces of the cube, perpendicular to the

x

-axis, is

The negative sign in Lenz's law indicates that the flow of current support the change in flux.

Important Questions on Electromagnetic Induction

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