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Faraday's law describes how electric fields and electromotive forces are generated from changing magnetic fields. This problem is a prototypical example in which an increasing magnetic flux generates a finite line integral of the electric field around a closed loop that surrounds the changing magnetic flux through a surface bounded by that loop. A cylindrical iron rod with cross-sectional area is oriented with its symmetry axis coincident with the z axis of a cylindrical coordinate system as shown. It has a uniform magnetic field inside that varies according to  .

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1. Find  , the electromotive force (EMF) around a loop that is at distance R from the z axis, where R is restricted to the region outside the iron rod as shown. Take the direction shown in the figure as positive

2. Due to the cylindrical symmetry of this problem, the induced electric field   can depend only on the distance R from the z axis, where R is restricted to the region outside the iron rod. Find this field

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Related textbook solutions

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

Related questions

Learning Goal: To work through astraightforward application of Faraday's law to find the EMF andthe electric field surrounding a region of increasing flux

Faraday's law describes how electric fields and electromotiveforces are generated from changing magnetic fields. This problem isa prototypical example in which an increasing magnetic fluxgenerates a finite line integral of the electric field around aclosed loop that surrounds the changing magnetic flux through asurface bounded by that loop. A cylindrical iron rod withcross-sectional area is oriented with its symmetry axis coincidentwith the z axis of a cylindrical coordinate system as shown. It hasa uniform magnetic field inside that varies according to . In otherwords, the magentic field is always in the positive z direction,and it has no other components.

For your convenience, we restate Faraday's law here: , where is theline integral of the electric field, and the magnetic flux is givenby , where is the angle between the magnetic field and the localnormal to the surface bounded by the closed loop.
Direction: The line integral and surface integral reverse theirsigns if the reference direction of or is reversed. The right-handrule applies here: If the thumb of your right hand is taken along ,then the fingers point along . You are free to take the loopanywhere you choose, although usually it makes sense to choose itto lie along the path of the circuit you are considering.

Find , the electromotive force (EMF) around a loop that is atdistance from the z axis, where is restricted to the region outsidethe iron rod as shown. Take the direction shown in the figure aspositive.
Express in terms of , , , , and any needed constants such as , ,and .
Due to the cylindrical symmetry of this problem, the inducedelectric field can depend only on the distance from the z axis,where is restricted to the region outside the iron rod. Find thisfield.
Express in terms of quantities given in the introduction (andconstants), using the unit vectors in the cylindrical coordinatesystem,r^ ,theta^ , and z^ .

Please answer either True or false and explain.

1. A large magnetic flux change through a coil must induce agreater emf in this coil than a small flux change.

2. A circular metal loop surrounds an ideal solenoid such that theplane of the loop is perpendicular to the cylindrical axis of thesolenoid. If the current in the solenoid is steadily increased, noemf is induced in the loop because the magnetic field outside anideal solenoid is zero.

3. When it is connected in a circuit, an inductor must resisthaving current flow through it.


Please explain, thanks

A coil of wire is connected to a power supply, and a currentruns in the coil. A single loop of wire is located near the coil,with its axis on the same line as the axis of the coil. The radiusof the loop is 2 cm.




At time t1 the magnetic field at the center of the loop, due to thecoil, is 0.4 T, in the direction shown in the diagram; the currentin the coil is constant.

(a) What is the absolute value of the magnetic flux through theloop at time t1?
Φ mag = T m2
(b) What approximations or assumptions did you make in calculatingyour answer to part (a)?

Check all that apply.

1.The magnitude of the magnetic field due to the coil is uniformover the area of the loop.
2.The magnetic field outside the loop is zero.
3. The magnetic field due to the coil is uniform in direction overthe area of the loop.


(c) What is the direction of the "curly" electric field inside thewire of the loop at time t1? (Remember that at this time thecurrent in the coil is constant.)
E = 0

At a later time t2, the current in the coil begins todecrease.

(d) Now what is the direction of the "curly" electric field in theloop?
counter-clockwise
At time t2 the rate of change of the magnetic field at the centerof the loop, due to the coil, is -0.36 T/s.
(e) At this time, what is the absolute value of the rate of changeof the magnetic flux through the loop?
|dΦmag/dt| = T m2/s
(f) At this time, what is the absolute value of the emf in theloop?
|emf| = V
(g) What is the magnitude of the electric field at location P,which is inside the wire?
|E| = V/m
(h) Now the wire loop is removed. Everything else remains as it wasat time t2; the magnetic field is still changing at the same rate.What is the magnitude of the electric field at location P?
|E| = V/m

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