Physics for IGCSE & O level - Magnets And Currents (Section 8)
1
What is the definition of a magnetic domain?
პასუხი
(B)
A small region of a magnetic material where the magnetic fields of the atoms are aligned.
2
Which of the following statements best describes the role of transformers in the power grid?
პასუხი
(C)
They change the voltage levels of AC power.
3
What is a solenoid?
პასუხი
(C)
A coil of wire.
4
What is the function of the magnetic field?
პასუხი
(B)
To exert a force on moving electric charges.
5
What factors increase the strength of a magnetic field in an electromagnet?
პასუხი
A
B
6
The units of electrical power are:
პასუხი
(C)
Watts
7
What can be used to strengthen an electromagnet?
პასუხი
A
B
C
8
What increases the strength of the magnetic field in a coil?
პასუხი
A
B
9
What type of current is used in the primary coil of a transformer?
პასუხი
(B)
Alternating current
10
What happens to the magnetic field of an electromagnet when you increase the current flowing through it?
პასუხი
(C)
The magnetic field becomes stronger
11
Which of the following items can be magnetized?
პასუხი
A
C
12
Which law explains the working of a transformer?
პასუხი
(B)
Faraday's law of electromagnetic induction
13
What are the losses that affect the efficiency of a transformer?
პასუხი
A
B
C
D
14
What are the main elements that determine the transformer's properties?
პასუხი
A
B
D
15
Which rule helps to determine the direction of the force on a current-carrying conductor placed in a magnetic field?
პასუხი
(B)
Fleming's Left-Hand Rule
16
How is the direction of the magnetic field defined?
პასუხი
(B)
The direction a compass needle will point
17
In a step-up transformer, what is the relationship between the number of turns in the primary and secondary coils?
პასუხი
(C)
Primary turns < Secondary turns
18
Which of these factors would affect the strength of a magnetic field produced by a solenoid?
პასუხი
B
C
D
19
How is sound produced by a moving-coil loudspeaker?
პასუხი
(C)
By the vibration of the cone.
20
What is the term for the process of removing magnetic properties from a material?
პასუხი
(B)
Demagnetization.
21
In which device is an electromagnet typically used?
პასუხი
(C)
A loudspeaker.
22
What type of transformer is used to safely isolate a circuit from the mains supply?
პასუხი
(C)
Isolation
23
What happens to the induced e.m.f. in the second coil when the current in the first coil reverses direction?
პასუხი
(B)
The e.m.f. is reversed.
24
What is the main function of the secondary coil in a transformer?
პასუხი
(C)
To supply electrical energy.
25
What is the effect of increasing the number of turns of wire on a coil in an electromagnet?
პასუხი
(B)
The magnetic field increases.
26
What is meant by 'turns ratio' of a transformer?
პასუხი
(B)
Ratio of primary coil turns to secondary coil turns
27
What is the direction of the magnetic field outside of a bar magnet?
პასუხი
(A)
From the north pole to the south pole.
28
In which direction does the current flow in a simple A.C. generator?
პასუხი
(B)
Reverses direction periodically.
29
If the number of turns in the primary coil of a transformer is increased, while keeping the number of turns in the secondary coil constant, what will happen to the output voltage?
პასუხი
(B)
Decrease
30
What are the main functions of a step up transformer?
პასუხი
(C)
Increase the voltage
31
What happens to the current in the secondary coil of a step-up transformer?
პასუხი
(B)
Decreases
32
How can you reverse the direction of the magnetic field in an electromagnet?
პასუხი
(C)
Reverse the direction of the current.
33
What is the benefit of using laminated core in transformers?
პასუხი
(A)
To reduce eddy current losses
34
What is the purpose of the iron core in a transformer?
პასუხი
(B)
To increase the efficiency of the transformer.
35
In a hard disk drive, what is used to write information onto the disk?
პასუხი
(B)
An electromagnet.
36
What is the role of the iron core in an electromagnet?
პასუხი
(B)
To increase the strength of the magnetic field.
37
In a moving-coil loudspeaker, what type of current does the amplifier send to the coil?
პასუხი
(B)
Alternating current (AC).
38
What is the role of the armature in an electric motor?
პასუხი
(B)
To rotate in the magnetic field.
39
What happens to the direction of the magnetic field when the direction of the current in a wire is reversed?
პასუხი
(C)
The field reverses direction.
40
Which statement best describes the magnetic field lines around a bar magnet?
პასუხი
(C)
They form closed loops, originating from the North pole and going to the South pole.
41
What happens to the force on a current-carrying wire in a magnetic field if the current is doubled?
პასუხი
(B)
The force is doubled.
42
What happens to the amount of e.m.f. in the second coil if the current in the first coil is switched off?
პასუხი
(A)
e.m.f. is induced.
43
When the coil in a simple generator is vertical, what is the current?
პასუხი
(B)
Zero
44
A transformer with a turns ratio of 1:5 is connected to a 120 V AC supply. Which of the following statements is correct about the output voltage?
პასუხი
A
C
45
What happens if two north poles of magnets are brought together?
პასუხი
(B)
They will repel each other.
46
What is the function of a commutator in an electric motor?
პასუხი
(A)
To reverse the current's direction.
47
What is induced magnetism?
პასუხი
(C)
Magnetism in a material caused by a nearby magnet.
48
In the context of generators, which type of electrical energy is typically produced?
პასუხი
(B)
Alternating Current (AC)
49
What is the purpose of a circuit breaker?
პასუხი
(C)
To switch off the current in a circuit when it is too high.
50
What factors contribute to power losses in a transformer?
