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23 Nov 2019

How can 2 be correct if 1 is correct?
We apply Lenz's law: The change in magnetic flux must be opposed bythe induced magnetic field.

1- At position number 1 the magnetic field caused by the wire isdirected out of the paper. The coil is moving into an area ofgreater magnetic field and closer to the wire. Thus, the fluxthrough the coil is increasing. According to Lenz's law thisincrease must be countered by the induced field. The direction ofthe induced field as a result goes into the paper. So, the currentin the coil is clockwise.

2- At position number 2 the magnetic field is going into the paperand decreasing as the coil is moving away from the wire. Again,according to Lenz's law the induced magnetic field must counter.Thus the induced field must go into the paper. As a result thecurrent in the coil is clockwise in this case also.

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Deanna Hettinger
Deanna HettingerLv2
5 Jan 2019

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

1a) Faraday discovered that a current is induced in a coil

A) only when the N pole of a magnet is inside the coil
B) only when the S pole of a magnet is inside the coil
C) only when there is a magnetic field inside the coil
D) only when the magnetic field inside the coil is changing

1b). A conductor moves through a uniform magnetic field at speed v and has a motional emf V created across it. If the conductor were to move twice as fast through the magnetic field, the motional emf would be:

A) V
B) 2V
C) 4V
D) V/2
E) V/4

1c) In the conducting rail discussed in section 25.2 (where the rail is moving at constant speed), what can you say about the power input due to the person pulling on the rail and the power dissipated in the resistance?

A) Power input from pull = power dissipated in R
B) Power input from pull > power dissipated in R
C) Power input from pull < power dissipated in R

1d) The electric generator as shown in the reading generates electricity by:

A) rotating a loop inside a magnetic field
B) moving a magnet in and out of a loop
C) sliding a loop over a magnet
D) running current through a loop in a magnetic field

1e) The magnetic flux through a loop:

A) is proportional to the number of magnetic field lines going through it
B) depends just on the B field going through the loop
C) is maximized when the B field lines in the plane of the loop
D) is zero when the B field is perpendicular to the plane of the loop
E) doesn't depend on the direction of the B field

1f) According to Lenz's Law, the induced B field (due to the induced current) will:

A) be in the opposite direction of the existing B field
B) be in the same direction as the existing B field
C) be in the same direction as the change in the existing B field
D) be in the opposite direction of the change in the existing B field

1g) A stationary coil experiences a doubling of its magnetic field (no change in direction of the field) in a time T and has a given induced EMF. If the same change were to have happened in half the time (T/2), the induced EMF would have been:

A) half as large
B) the same
C) twice as large
D) one-fourth as large
E) four times as large

1h) Eddy currents:

A) make it hard to pull a nonmagnetic material through a magnetic field
B) make it hard to pull a magnetic material through a magnetic field
C) speed up a magnetic material moving through a magnetic field
D) speed up a nonmagnetic material moving through a magnetic field

 

 

x.Hme magnetic flux through a certain region is changing with time:

1
energy must bedissipated as heat an electric field mustexist at theboundary an emf must existaround theboundary a current must flowaround the boundary

A square loop of wire lies in the plane of the page. Adecreasingmagnetic field is directed into the page. The inducedcurrent in theloop is:
1
clockwise counterclockwise clockwise in twoofthe loop sides and counterclockwise in the other two zero dependsupon whether or not B is decreasing at aconstantrate

As an externally generated magnetic field through a certainconductingloop increases in magnitude, the field produced at pointsinside theloop by the current induced in the loop must be:
1
increasing inmagnitude decreasinginmagnitude in the same directionas theapplied field directed opposite tothe applied field perpendicularto theapplied field

As an externally generated magnetic field through a certainconductingloop increases in magnitude, the field produced at pointsinside theloop by the current induced in the loop must be:
1
increasing inmagnitude decreasinginmagnitude in the same directionas theapplied field directed opposite tothe applied field perpendicularto theapplied field

A long straight wire is in the plane of a rectangular conductingloop.The straight wire carries a constant current i, asshown. Whilethe wire is being moved toward the rectangle thecurrent in therectangle is:



1
zero counterclockwise clockwise in theleftside and counterclockwise in the right side counterclockwiseinthe left side and clockwise in the right side clockwise

The emf developed in a coil "X" due to the current in a neighboringcoil"Y" is proportional to the:
1
rate of change ofmagnetic field in X thickness of the wireinX magnetic field in Xcurrent in Yresistance of X

In the experiment shown:



1
since the two loopsare not connected, the current in G is alwayszero there is a steadyreading in G as long as S isclosed the current in thebattery goesthrough G there is a current

You are given a circular conducting wire loop with one
end cut out and connected to a resistor, R, as shown in
the figure to the right. A metal rod of length l is set at an
initial angle ?0 from the resistor, and then rotates
clockwise about the center of the wire loop with angular
frequency through a uniform magnetic field B
directed into the page. The metal rod stays in contact
with the wire loop at all points of its motion. Unless
otherwise requested, all answers should be in simplified
algebraic form using the above given variables.

(a) Given that the initial angle ?0 is in radians, what is theinitial area of the closed circuit “wedge”defined by ?0? (2pts.)
(b) What is the magnetic flux through this initial “wedge” areadefined by ?0? (2 pts.)
Starting at time t=0 at position ?0, the rod is rotated clockwisewith angular velocity as shown in
the figure. Given this configuration, answer questions (c)-(g)below:
(c) What is the direction of the induced magnetic field inside the“wedge”? (2 pts)
(d) What is the direction of the induced current around the closedcircuit? (2 pts)
(e) What is the magnitude of the induced emf, E in the circuit? (4pts)
(f) What is the magnitude of the induced current in the circuit? (4pts)
(g) What is the power used by the resistor? (4 pts)
(h) The metal rod is now rotated in the opposite direction, i.e. inthe counter-clockwise direction. Given this information, completethe chart below as to what quantities you just calculated change,and what ones do not change. You do not have to show work, justgive the result. No partial credit will be given here. (5pts)

Direction of induced magnetic field inside the “wedge”.
Direction of the induced current around the closed circuit.
Magnitude of the induced emf, E in the circuit.
Magnitude of the induced current in the circuit.
Power used by the resistor.


The setup is now modified slightly so that the circular conductingwire loop no longer has a small
section removed as shown in both figures below. This modificationwould allow the metal rod to
continuously rotate on the circular wire loop as clearlyillustrated in the 3D side view. The metal rod
is rotated clockwise, as in the initial part of the problem.


(i) Given this information, complete the chart below. You do nothave to show work, just give the
result. No partial credit will be given here. (5 pts)

Direction of induced magnetic
field inside the “wedge”.
Direction of the induced current
around the closed circuit.
Magnitude of the induced emf, E in
the circuit.
Magnitude of the induced current
in the circuit.
Power used by the resistor.

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