Download Homework Journal Problems 11 for Hacker

Physics 215 – Fall 2006
Name: ______________________
Homework Journal #11:
Electromagnetic Induction
Instructor: Capt Hacker
Section:
M3 M4 M6
Date Due: M27
INSTRUCTIONS: To receive full credit, you must fully justify your answers and show all written
work (including algebraic steps) in a neat and orderly fashion. If your work is disorganized or the
grader cannot follow your logic, you will be penalized. Avoid writing down single answer solutions –
the homework problems, like the GRs, are generally designed to require multiple steps and, with only a
few exceptions, are not “plug and chug” exercises.
AUTHORIZED RESOURCES: Please document any instructor(s) and/or student(s) you consulted
and the precise nature of the assistance you received in completing this assignment. You DO NOT
need to document use of the text, class handouts, or your own classroom instructor. Any published or
unpublished material, or internet source, does not need to be documented unless the material
specifically aims at answering problems.
DOCUMENTATION:
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
Problem Name
Points
Possible
Points
Earned
Problem Name
Knight Problem 33.10
Light Bulb and
Induced emf
Knight Problem 33.11
Knight Problem 33.44
Knight Problem 33.12
Electric Generator
Wire Loop in B-Field
Total:
_______
1/10
Points
Possible
Points
Earned
Problem Name: Knight Problem 33.10
Description: Each figure shows a 15-cm-diameter loop in three different magnetic fields and three
different orientations to the field. The loop's resistance is 0.3 
Part A: Determine the magnitude of the induced emf for figure (a).
Answer:
Part B: Determine the induced current for figure (a).
Answer:
Part C: Determine the direction of the current.
Answer:
Physics 215 – Fall 2006
2/10
Homework Journal #11
Part D: Determine the magnitude of the induced emf for figure (b).
Answer:
Part E: Determine the induced current for figure (b).
Answer:
Part F: Determine the magnitude of the induced emf for figure (c).
Answer:
Part G: Determine the magnitude of the induced emf for figure (c).
Answer:
Part H: Determine the induced current for figure (c).
Answer:
Part I: Determine the direction of the current.
Answer:
Physics 215 – Fall 2006
3/10
Homework Journal #11
Problem Name: Knight 33.11
Description: An 1100-turn coil of wire that is 2.20 cm in diameter is in a magnetic field that drops
from 0.130 T to 0 T in 10.0 ms. The axis of the coil is parallel to the field.
Part A: What is the emf of the coil?
Answer:
Physics 215 – Fall 2006
4/10
Homework Journal #11
Problem Name: Knight 33.12
Description: The loop in the figure is being pushed into the 0.20 T magnetic field at 50 m/s. The
resistance of the loop is 0.10 .

Part A: What is the magnitude of the current in the loop?
Answer:
Part B: What is the direction of the current in the loop?
Answer:
Physics 215 – Fall 2006
5/10
Homework Journal #11
Problem Name: Wire Loop in B-Field
Description: A length of wire is formed into a single circular loop and placed in a uniform magnetic
field as shown. The radius of this loop is 0.30 m and the resistance of the wire is 0.90 . The strength
of the magnetic field increases in time according to the expression:
B(t) = (0.25 + 0.725t) T.
Part A: What is the magnitude of the magnetic flux through the loop at time t = 0 s?
Answer:
Part B: What is the magnitude of the average induced electromotive force (emf) from t = 0 to 1.9 s?
Answer:
Part C: In what direction will current flow in the loop during the interval from t = 0 to 1.9 s?
Answer:
Part D: If a different type of wire of the same length but greater resistance were used, what would be
the effect on the induced emf? (greater, less, same)
Answer:
Part E: If the same wire was looped twice instead of once, the radius of the resulting coil would be half
the original radius. What would be the total magnetic flux through this coil at t = 0 s?
Answer:
Physics 215 – Fall 2006
6/10
Homework Journal #11
Problem Name: Light Bulb and Induced emf
Description: A square wire loop 1.5 m on a side is connected to an 8 V light bulb in a uniform 4.5 T
magnetic field as shown. The magnitude of the magnetic field is reduced steadily to zero over a time
Δt.
Part A: What is the direction of induced current flow around the loop during the time Δt?
Answer:
Part B: For the light to shine at its full voltage rating (8 V), what should be the rate of change of the
magnetic flux?
Answer:
Part C: Find Δt such that the light will shine at its full voltage rating.
Answer:
Part D: Does the wire loop experience a torque during the time Δt?
Answer:
Part E: During the time Δt that the magnetic field is changing, what is the direction of the induced
electric field?
Answer:
Physics 215 – Fall 2006
7/10
Homework Journal #11
Problem Name: Knight 33.44
Description: The 10-cm-wide, zero-resistance slide wire shown in the figure is pushed toward the 2.0
resistor at a steady speed of 0.50 m/s. The magnetic field strength is 0.50 T.
Part A: How big is the pushing force?
Answer:
Part B: How much power does the pushing force supply to the wire?
Answer:
Physics 215 – Fall 2006
8/10
Homework Journal #11
Part C: What is the magnitude of the induced current?
Answer:
Part D: What is the direction of the induced current?
Answer:
Part E: How much power is dissipated in the resistor?
Physics 215 – Fall 2006
9/10
Answer:
Homework Journal #11
Problem Name: Electric Generator
Description: A round coil (21 turns of wire, 16 cm) is situated in a 0.2 T magnetic field. The coil
turns 90º in 0.02 sec.
Part A: What is the voltage induced in the coil?
Answer:
Part B: If the coil has 7  of resistance in it, what is the average current in the loop during the 0.02 s?
Answer:
Part C: In which direction is the current flowing in the picture above?
Answer:
Physics 215 – Fall 2006
10/10
Homework Journal #11