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1. (JEE Main 2024 (Online) 1st February Morning Shift)

A rectangular loop of sides 12   cm and 5   cm , with its sides parallel to the x -axis and y -axis respectively, moves with a velocity of 5   cm / s in the positive x axis direction, in a space containing a variable magnetic field in the positive z direction. The field has a gradient of 10 3   T / cm along the negative x direction and it is decreasing with time at the rate of 10 3   T / s . If the resistance of the loop is 6   m Ω , the power dissipated by the loop as heat is __________ × 10 9   W .

Correct answer is 216

JEE Main 2024 (Online) 1st February Morning Shift Physics - Electromagnetic Induction Question 15 English Explanation

B 0 is the magnetic field at origin

d B d x = 10 3 10 2 B 0 B d B = 0 x 10 1 d x B B 0 = 10 1 x B = ( B 0 x 10 )

Motional emf in AB = 0

Motional emf in CD = 0

Motional emf in AD = ε 1 = B 0 v

Magnetic field on rod BC B

= ( B 0 ( 12 × 10 2 ) 10 )

Motional emf in BC = ε 2 = ( B 0 + 12 × 10 2 10 ) × v

ε eq = ε 2 ε 1 = 300 × 10 7   V

For time variation

( ε eq  ) = A dB dt = 60 × 10 7   V ( ε eq ) net  = ε eq + ( ε eq ) = 360 × 10 7   V  Power  = ( ε eq  ) net  2 R = 216 × 10 9   W

2. (JEE Main 2024 (Online) 30th January Morning Shift)

A ceiling fan having 3 blades of length 80   cm each is rotating with an angular velocity of 1200 rpm . The magnetic field of earth in that region is 0.5 G and angle of dip is 30 . The emf induced across the blades is N π × 10 5   V . The value of N is _________.

Correct answer is 32

B v = B sin 30 = 1 4 × 10 4 ω = 2 π × f = 2 π 60 × 1200   rad / s ε = 1 2 B V ω 2 = 32 π × 10 5   V

3. (JEE Main 2024 (Online) 29th January Evening Shift)

A horizontal straight wire 5   m long extending from east to west falling freely at right angle to horizontal component of earths magnetic field 0.60 × 10 4   Wbm 2 . The instantaneous value of emf induced in the wire when its velocity is 10   ms 1 is _________ × 10 3   V .

Correct answer is 3

B H = 0.60 × 10 4   Wb / m 2  Induced emf e = B H v = 0.60 × 10 4 × 10 × 5 = 3 × 10 3   V

4. (JEE Main 2023 (Online) 8th April Evening Shift )

An emf of 0.08   V is induced in a metal rod of length 10   cm held normal to a uniform magnetic field of 0.4   T , when moves with a velocity of:

A. 20   ms 1

B. 2   ms 1

C. 3.2   ms 1

D. 0.5   ms 1

Correct Option is (B)

The emf induced in a rod moving through a magnetic field is given by Faraday's law of electromagnetic induction, specifically, in the form of motional emf, which states that:

emf = B L v

where:

  • (B) is the magnetic field strength,
  • (L) is the length of the rod, and
  • (v) is the velocity of the rod.

In this case, we are given the emf, (B), and (L), and we need to solve for (v). Rearranging the equation gives:

v = emf B L

Substituting the given values:

v = 0.08 V 0.4 T × 0.1 m = 2 m/s

5. (JEE Main 2023 (Online) 25th January Evening Shift)

A wire of length 1m moving with velocity 8 m/s at right angles to a magnetic field of 2T. The magnitude of induced emf, between the ends of wire will be __________.

A. 20V

B. 8V

C. 16V

D. 12V

Correct Option is (C)

JEE Main 2023 (Online) 25th January Evening Shift Physics - Electromagnetic Induction Question 35 English Explanation
Induced emf across the ends = Bv l

= 2 × 8 × 1 = 16 V