Download presentation

Presentation is loading. Please wait.

1
Induction experiments(sec. 29.1) Faraday’s law (sec. 29.2) Lenz’s law(sec. 29.3) Motional electromotive force(sec. 29.4) Induced electric fields(sec. 29.5) Displacement Current(sec. 29.7) Electromagnetic Induction Ch. 29 C 2009 J. Becker

2
Current induced in a coil.

4
When B is constant and shape, location, and orientation of coil does not change, the induced current is zero.

5
Conducting loop in increasing B field.

6
Magnetic flux through an area.

7
Lenz’s law Lenz’s Law: The induced emf or current always tends to oppose or cancel the change that caused it.

8
Faraday’s Law of Induction How electric generators, credit card readers, and transformers work. A changing magnetic flux causes (induces) an emf in a conducting loop. C 2004 Pearson Education / Addison Wesley

9
Changing magnetic flux through a wire loop.

10
Alternator (AC generator) = 90 o

11
DC generator = 90 o

12
Slidewire generator

13
Magnetic force (F = IL x B) due to the induced current is toward the left, opposite to v.

14
Lenz’s law Lenz’s Law: The induced emf or current always tends to oppose or cancel the change that caused it.

15
Currents (I) induced in a wire loop.

16
Motional induced emf ( e ): e = v B L because the potential difference between a and b is e = D V = energy / charge = W/q e = D V = work / charge D V = F x distance / q D V = (q v B) L / q so e = v B L Length and velocity are perpendicular to B

17
Solenoid with increasing current I which induces an emf in the (yellow) wire. An induced current I’ is moved through the (yellow) wire by an induced electric field E in the wire.

18
Eddy currents formed by induced emf in a rotating metal disk.

19
Metal detector – an alternating magnetic field Bo induces eddy currents in a conducting object moved through the detector. The eddy currents in turn produce an alternating magnetic field B’ and this field induces a current in the detector’s receiver coil.

20
A capacitor being charged by a current i c has a displacement current equal to i C between the plates, with displacement current i D = e A dE/dt. This changing E field can be regarded as the source of the magnetic field between the plates.

21
A capacitor being charged by a current i C has a displacement current equal to i C between the plates, with displacement current i D = e A dE/dt From C = e A / d and D V = E d we can use q = C V to get q = ( e A / d ) (E d ) = e E A = e F E and from i C = dq / dt = e A dE / dt = e d F E / dt = i D We have now seen that a changing E field can produce a B field, and from Faraday’s Law, a changing B field can produce an E field or emf. C 2009 J. Becker

22
MAXWELL’S EQUATIONS C 2004 Pearson Educational / Addison Wesley The relationships between electric and magnetic fields and their sources can be stated compactly in four equations, called Maxwell’s equations. Together they form a complete basis for the relation of E and B fields to their sources.

23
Lenz’s law (Exercise 29.16) Determine direction of induced current for a) increasing B b) decreasing B

24
Lenz’s law (Exercise 29.17)

25
Lenz’s law (Exercise 29.18)

26
Motional emf and Lenz’s law (Exercise 29.22)

27
Motional emf and Lenz’s law (Exercise 29.25)

28
See www.physics.edu/becker/physics51 Review C 2009 J. Becker

Similar presentations

© 2019 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google