Chapter 21: Faraday's Law on Electromagnetism Flashcards
Faraday’s law of induction states that the emf induced in a loop of wire is proportional to ________
The time variation of the magnetic flux
Doubling the number of loops of wire in a coil produces what kind of change on the induced emf, assuming all other factors remain constant?
The induced emf is twice times as much.
Doubling the strength of the magnetic field through a loop of wire produces what kind of change on the induced emf, assuming all other factors remain constant?
The induced emf is twice as much
Doubling the diameter of a loop of wire produces what kind of change on the induced emf, assuming all other factors remain constant?
The induced emf is 4 times as much.
An electric generator transforms ________
mechanical energy into electrical energy.
A transformer is a device used to ________
increase or decrease an ac voltage.
A transformer is a device that ________
operates only on AC
In a transformer, if the primary coil contains more loops than the secondary coil then it is a ________
step-down transformer
A flux of 4.0 x 10^-5 Wb is maintained through a coil for 0.50 s. What emf is induced in this coil by this flux?
No emf induced in this coil.
A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are parallel.
zero
A circular loop of radius 0.10 m is rotating in a uniform magnetic field of 0.20 T. Find the magnetic flux through the loop when the plane of the loop and the magnetic field vector are perpendicular.
6.3 x 10^-3 T*m2
The cross-sectional area of an adjustable single loop is reduced from 1.0 m2 to 0.50 m2 in 0.10 s. What is the average emf that is induced in this coil if it is in a region where B = 2.0 T upward, and the coil’s plane is perpendicular to B?
10 V
The flux through a coil changes from 4.0 x 10^-5 Wb to 5.0 x 10^-5 Wb in 0.10 s. What emf is induced in this coil?
1 x 10^-4 V
A step-down transformer is needed to reduce a primary voltage of 120 V AC to 6.0V AC. What turns ratio is required?
20:1
In a transformer, how many turns are necessary in a 110-V primary if the 24-V secondary has 100 turns?
458
The secondary coil of a neon sign transformer provides 7500 V at 10.0 mA. The primary coil operates on 120 V. What does the primary draw?
0.625 A
The primary of a transformer has 100 turns and its secondary has 200 turns. If the input current at the primary is 100 A, we can expect the output current at the secondary to be ________
50 A
The primary of a transformer has 100 turns and its secondary has 200 turns. If the input voltage to the primary is 100 V, we can expect the output voltage of the secondary to be ________
200 V
In order to change the magnetic flux through the loop, what would you have to do to the magnet?
A. drop the magnet
B. move the magnet upward
C. move the magnet sideways
D. either A or B
E. all of the above
all of the above
B
The moving rod in the figure below is 13.2 cm long and generates a motional emf of 120 mV while moving in a 0.90-T magnetic field. What is its speed?
no induced current
A generator has a coil of wire rotating in a magnetic field. If the rotation rate increases, what happens to the maximum (peak) output voltage of the generator?
it increases
The generator of a car idling at 875-rpm produces 12.4 V. What will the output be at a rotation speed of 1550 rpm, assuming nothing else changes?
The first transformer coil is connected to a 120-V ac outlet. What is the voltage across the lightbulb?
120 V
step-up transformer
the secondary coil contains more loops than the
primary coil does
step-down transformer
the secondary coil contains less loops than the
primary does
Given that the intermediate current is 1 A, what is the current through the lightbulb?
2 A
Neon signs require 12 kV for their operation. (a) To operate from a 240−V line, what must be the ratio of secondary to primary turns of the transformer? (b) What would be the voltage output if the transformer were connected backward?
