PHYC10007 Lecture Notes - Lecture 29: Galvanometer, Electric Field

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roseturtle504

6 Oct 2018

School

University of Melbourne

Department

Physics

Course

PHYC10007

Professor

Chris Chantler

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Document Summary

Induced currents fa(cid:396)ada(cid:455)(cid:859)s law: an electric field can produce a magnetic field, a changing magnetic field induces an electric current, cu(cid:396)(cid:396)e(cid:374)t i(cid:374)du(cid:272)ed i(cid:374) a (cid:272)losed loop of wi(cid:396)e that (cid:858)su(cid:396)(cid:396)ou(cid:374)ds(cid:859) the (cid:272)ha(cid:374)gi(cid:374)g magnetic field. I(cid:374) fa(cid:396)ada(cid:455)(cid:859)s o(cid:396)igi(cid:374)al e(cid:454)pe(cid:396)i(cid:373)e(cid:374)t, the (cid:374)o(cid:396)th pole of a pe(cid:396)(cid:373)a(cid:374)e(cid:374)t (cid:271)a(cid:396) (cid:373)ag(cid:374)et (a magnetized piece of iron) is moved through a conductor loop: as a result, the galvanometer displays a current peak. Induced electric field is larger if magnetic field is more intense: magnetic flux, depends on the angle between wire loop and magnetic field. Imagine a fan blowing air through a loop, more air through loop when loop is perpendicular to air flow. If two planes are parallel no induction. If there are n turns of wire enclosing the magnetic flux, the equation becomes: generators, pulling the loop of wire in a magnetic field to.

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