JAMB Exam  >  JAMB Notes  >  Physics for JAMB  >  Motional Electromotive Force

Motional Electromotive Force | Physics for JAMB PDF Download

Motional Electromotive Force

An emf induced by the motion of the conductor across the magnetic field is a motional electromotive force. The equation is given by E = -vLB.  This equation is true as long as the velocity, field, and length are mutually perpendicular. The minus sign associated with the Lenz’s law.
Motional Electromotive Force | Physics for JAMB

For us to understand the motional electromotive force, let us make a particular setup. Let us take a rectangular coil, a metal rod of length L, moving with velocity V, through a magnetic field B. There is a magnetic field at some location.
Length, velocity and magnetic field should always be at a right angle with each other. The direction of the magnetic field is going inside. Assume the metal rod is frictionless that means there is no loss of energy due to friction and we apply a uniform magnetic field. The conductor rod is moved with a constant velocity and placed in the magnetic field.

Browse more Topics under Electromagnetic Induction

ΦB = Blx

  • AC Generator
  • Eddy Currents
  • Energy Consideration: A Quantitative Study
  • Faraday’s and Lenz’s Law
  • Inductance

But ‘x’ changes with time,

Motional Electromotive Force | Physics for JAMBE = Blv
The induced emf Blv is motion electromotive force. So we produce emf by moving a conductor inside the uniform magnetic field. The power required to move a conductor rod in a magnetic field is,
Motional Electromotive Force | Physics for JAMB

Where,

  • B is the magnetic field,
  • l is the length of the conductor
  • v is the velocity of the conductor
  • R is the resistance

The magnetic flux associated with the coil is given by Φ = BA cos θ. We know that cos θ = 0, so Φ = BA. The motion of electromotive force can be further explained by Lorentz force which acts on free charge carriers. The Lorentz force on charge is:
F = qVB

Solved Questions

Q.1. A coil having n turns and area A is initially placed with its plane normal to the magnetic field B. It is then rotated through 180º in 0.2 sec. The emf induced at the ends of the coils is
(a) 0.1 nAB
(b) nAB
(c) 5 nAB
(d) 10 nAB
Ans: (d)
Solution: Total change in flux = ΔΦ = 2 nAB
Total time of change = Δt = 0.2s
Emf induced = ΔΦ/Δt = 10nAB

Q.2. A straight line conductor of length 0. 4m is moved with a speed of 7ms-1 perpendicular to a magnetic field of an intensity of 0.9wbm-2 The induced emf across the conductor is:
(a) 25.2 V
(b) 5.24 V
(c) 2.52 V
(d) 1.26 V
Ans:
(c)
Solution: The induced emf across the conductor E= Blv
= 0.98 × 0.4 × 7 = 2.52V

Q.3. Two conducting rings of radii r and 2r move in opposite directions with velocities 2v and v respectively on a conducting surface S. There is a uniform magnetic field of magnitude B perpendicular to the plane of the rings. The potential difference between the highest points of the two rings is:
(a) Zero
(b) 2rvB
(c) 4rvB
(d) 8rvB
Ans: (d)
Solution: Replace the emf in the rings by the cells.
E1= B2r(2V) = 4Brv 
E= B(4r)v  = 4Brv 
V–  V= 8Brv 

The document Motional Electromotive Force | Physics for JAMB is a part of the JAMB Course Physics for JAMB.
All you need of JAMB at this link: JAMB
Are you preparing for JAMB Exam? Then you should check out the best video lectures, notes, free mock test series, crash course and much more provided by EduRev. You also get your detailed analysis and report cards along with 24x7 doubt solving for you to excel in JAMB exam. So join EduRev now and revolutionise the way you learn!
Sign up for Free Download App for Free
261 videos|249 docs|232 tests

Up next

FAQs on Motional Electromotive Force - Physics for JAMB

1. What is motional electromotive force?
2. How is motional electromotive force calculated?
Ans. Motional electromotive force can be calculated using the formula E = B * L * v, where E is the induced voltage, B is the magnetic field strength, L is the length of the conductor perpendicular to the magnetic field, and v is the velocity of the conductor.
3. What is the significance of motional electromotive force?
Ans. Motional electromotive force is important in various applications, such as electric generators and motors. It plays a crucial role in converting mechanical energy into electrical energy and vice versa.
4. How does motional electromotive force impact electric generators?
Ans. In electric generators, motional electromotive force is used to produce electricity. When a conductor (such as a coil of wire) is rotated in a magnetic field, the motional electromotive force induces a voltage, which leads to the generation of electrical power.
5. What factors affect the magnitude of motional electromotive force?
Ans. The magnitude of motional electromotive force depends on several factors, including the strength of the magnetic field, the length of the conductor, and the velocity at which the conductor moves through the magnetic field. Increasing any of these factors will result in a higher induced voltage.
261 videos|249 docs|232 tests
Download as PDF

Up next

Explore Courses for JAMB exam
Related Searches

past year papers

,

Summary

,

Sample Paper

,

Semester Notes

,

Important questions

,

Extra Questions

,

ppt

,

Viva Questions

,

Free

,

Motional Electromotive Force | Physics for JAMB

,

practice quizzes

,

mock tests for examination

,

Exam

,

shortcuts and tricks

,

Motional Electromotive Force | Physics for JAMB

,

MCQs

,

Previous Year Questions with Solutions

,

video lectures

,

Objective type Questions

,

Motional Electromotive Force | Physics for JAMB

,

study material

,

pdf

;