Phys 133 -- Chapter 33 1
Chapter 33
Electromagnetic Induction
Phys 133 -- Chapter 33 2
Demo Faraday
Phys 133 -- Chapter 33 3
Some experiments
Phys 133 -- Chapter 33 4
Motional emf
Phys 133 -- Chapter 33 5
Motional emf (cont.)Reach equilibrium
Phys 133 -- Chapter 33 6
A potential difference of 0.050 V is developed across a 10-cm long wire as it moves through a magnetic field at 5.0 m/s. The magnetic field is perpendicular to the wire axis. What are strength and direction of field?
Problem 33.1
Phys 133 -- Chapter 33 7
Problem 33.1 (ans)At equilibrium
FeFm
Out of page
Phys 133 -- Chapter 33 8
--moving charges in B field, force --> current
--current-carrying wire in field, force
Induced current
Phys 133 -- Chapter 33 9
Do workbook 33.1
Phys 133 -- Chapter 33 10
Eddy currents
Phys 133 -- Chapter 33 11
Do workbook 33.2 & 4
Phys 133 -- Chapter 33 12
Eddy currents (cont.)
Phys 133 -- Chapter 33 13
Demo eddy currents
Phys 133 -- Chapter 33 14
Do workbook 33.5 & 7
33.5 & 7
Phys 133 -- Chapter 33 15
Magnetic flux
Phys 133 -- Chapter 33 16
Do workbook 33.9 & 11
Phys 133 -- Chapter 33 17
There is an induced current in a closed, conducting loop if and only if the magnetic flux through the loop is changing. The induced current creates an induced magnetic field which opposes the change in flux.
--changing flux produces induced current
--induced current creates induced field
--induced field opposes the change
Lenz’s law
Phys 133 -- Chapter 33 18
Do workbook 33.12, 13 & 19
Phys 133 -- Chapter 33 19
The current in the solenoid is decreasing. The solenoid is surrounded by a conducting loop. Is there a current in the loop? If so, is the current in the loop cw or ccw?
Problem 33.9
Phys 133 -- Chapter 33 20
Problem 33.9 (ans)
B1
Initially
later
B2
∆Change in flux to left
• Find change in flux
• Find induced field
Induced field points to right
• Find induced currentInduced current is clockwise from behind
Phys 133 -- Chapter 33 21
field is there independent of wireInduced fields
Phys 133 -- Chapter 33 22
--law of nature
--usually helpful
Faraday’s law
-field can change
-area can change
-both can change
Phys 133 -- Chapter 33 23
Do workbook 33.21
Phys 133 -- Chapter 33 24
Problem 33.12bThe loop is being pushed out of the 0.20 T magnetic field at 50 m/s. The resistance of the loop is 0.20 . What are the direction and magnitude of current in the loop?
Phys 133 -- Chapter 33 25
Problem 33.12b (ans)
L
w
Counter-clockwise
Phys 133 -- Chapter 33 26
Two 20-turn coils are tightly wrapped on the same 2.0-cm-diameter cylinder with 1.0-mm-diameter wire. The current through coil 1 is shown. A positive current is into the page at the top of the loop. Determine the current in coil 2 as current vs. time t = 0 s to 0.4 s. (Assume field of coil 1 passes completely through coil 2.
0.1 0.3
Problem 33.35
Phys 133 -- Chapter 33 27
Problem 33.35 (ans)
B1
(+)
2
I1
d2/dt
2
I2
Phys 133 -- Chapter 33 28
Problem 33.35 (ans)
(+)
I1
I2
Right to left through resistor
Phys 133 -- Chapter 33 29
Generator
Phys 133 -- Chapter 33 30
Transformer
Phys 133 -- Chapter 33 31
Coulomb and non-Coulomb electric fields
Phys 133 -- Chapter 33 32
-symmetric in E and B
Maxwell and induced magnetic field
Phys 133 -- Chapter 33 33
E & M equations
Phys 133 -- Chapter 33 34
Maxwell’s equations
Phys 133 -- Chapter 33 35
+math
Light is an E&M wave!!!
Maxwell-no charges or current
Phys 133 -- Chapter 33 36
EM waves
Phys 133 -- Chapter 33 37
Problem 33.49A U-shaped conducting rail that is oriented
vertically in a horizontal magnetic field. The rail has no electrical resistance and does not move. A slide wire with mass m and resistance R can slide up and down without friction while maintaining electrical contact with the rail. The slide wire is release from rest.
a) Describe the motion of the slide wire.b) Find the terminal velocity of the slide wire