Download Chapter 29:Electromagnetic Induction and Faraday*s Law

Chapter 29:Electromagnetic
Induction and Faraday’s Law
Chapter 29: 3,30,48
Chapter 30 :4, 10,33
Due on Wednesday, April 5
Problem 17
17. (II) The magnetic field perpendicular
to a single 18.2-cm-diameter circular loop
of copper wire decreases uniformly from
0.750 T to zero. If the wire is 2.35 mm in
diameter, how much charge moves past a
point in the coil during this operation?
29-3 EMF Induced in
a Moving Conductor
This image shows another way the
magnetic flux can change:
29-3 EMF Induced in a
Moving Conductor
The induced emf has magnitude
This equation is valid as long as B, ,and v
are mutually perpendicular (if not, it is
true for their perpendicular components).
29-3 EMF Induced in a
Moving Conductor
The induced current is in a direction that
tends to slow the moving bar – it will take
an external force to keep it moving.
29.3 Motional EMF
1. Moving rod in B-Field --> Electrons experience FB
2. electrons move in the direction of FB creating a
charge separation and E-field
3. Electric Force FE balances FB
FE
FB
-
+
E
-
L
v
B
equilibrium
FE = FB
-eE = -ev ´ B
E = vB Þ DV=EL = LvB
29-3 EMF Induced in a Moving Conductor
Example 29-8: Force on the rod.
To make the rod move to the right at speed v, you need to apply an
external force on the rod to the right. (a) Explain and determine the
magnitude of the required force. (b) What external power is needed
to move the rod?
Problem 33
33.(II) A conducting rod rests on two long frictionless parallel rails in a magnetic
field B (┴ to the rails and rod) as in Fig. 29–44. (a) If the rails are horizontal and
the rod is given an initial push, will the rod travel at constant speed at the
beginning of the motion even though a magnetic field is present? (b) Suppose at
t=0 when the rod has speed v=v0 the two rails are connected electrically by a wire
from point a to point b. Assuming the rod has resistance R and the rails have
negligible resistance, determine the speed of the rod as a function of time.
a
Discuss your answer.
b