PHYSICS 1E03 Chapter Notes - Chapter 31: Ammeter, Circuit Diagram, Angular Frequency

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scarletsea-lion793

18 Apr 2017

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This current only exists so long as the magnetic field changes: can be written mathematically: , or if a coil consists of n loops with the same area in series : emf can be induced in the circuit several ways: The magnitude of b can change with time. The area enclosed by the loop can change with time. The angle between b and the normal to the loop can change with time. Motional emf induced in a rotating bar: a conducting bar of length l rotates with constant angular speed about a pivot at one end. B is directed perpendicular to the plane of rotation: we get the formula, after integrating: In the example previous, with the sliding bars, we saw how the magnetic flux due to an external field directed into the page is increasing; therefore, the induced current must produce a field out of the page.

Related Questions

A loop of wire is lying flat on a tabletop. A uniform magneticfield is directed vertically UPWARDS such that it is perpendicularto the tabletop (and the loop) and pointing toward the ceiling.Beyond the edges of the table, the magnetic field is zero. Imaginethat you are looking DOWN on the loop from above. Which of thefollowing statements are true about the induced EMF in the wireloop?

1)If the magnetic field suddenly decreases, the induced currentwill be in a counter-clockwise direction.
2)If the magnetic field suddenly decreases, the induced currentwill be in a clockwise direction.
3)If the loop suddenly shrinks in size, the induced current will bein a clockwise direction.
4)If you pull the loop out of the field, by sliding it off thetable, the induced current will be in a clockwise direction.
5)Lenz's Law states that the induced current always leads to amagnetic field that OPPOSES the change in magnetic flux.
6)If you keep the loop on the table, but pull it to the right,there will be no induced current.

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

cerisejackal809

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

PHYSICS 1E03 Chapter Notes - Chapter 31: Ammeter, Circuit Diagram, Angular Frequency

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