Physics for IGCSE & O level - Magnets And Currents (Section 2)
1
What is the direction of a magnetic field?
پاسخ دهید(A)
From the north pole to the south pole
2
In a well-designed transformer, what is the relationship between input and output power (neglecting losses)?
پاسخ دهید(C)
Input power equals output power.
3
What is used for the mains?
پاسخ دهید(A)
Alternating current (a.c.)
4
Which statement best describes a motor?
پاسخ دهید(A)
A device that converts electrical energy to mechanical energy.
5
Which materials are most strongly attracted to a magnet?
6
What is the function of the core in a transformer?
پاسخ دهید(B)
To provide a path for the magnetic field
7
What is the role of a magnetic relay in a circuit?
پاسخ دهید(B)
To allow a small current to control a larger one.
8
How can the direction of the force on a wire be predicted?
پاسخ دهید(C)
Using Fleming's left-hand rule.
9
What is the purpose of the brushes in a DC motor?
پاسخ دهید(A)
To make contact with the rotating commutator.
10
What happens when a current-carrying wire is placed in a magnetic field?
پاسخ دهید(B)
A force is exerted on the wire
11
What is the key difference between slip rings and a commutator?
پاسخ دهید(A)
Slip rings are for AC, and commutators are for DC.
12
What are the main components in a practical transformer?
13
Which of the following are factors that influence the strength of the magnetic field of an electromagnet?
14
What component in a DC motor is used to reverse the current's direction and keep the motor spinning?
15
What are the main objectives of a cross-country power transmission system?
16
Which is the best description of induced magnetism?
پاسخ دهید(C)
Magnetism created by the presence of another magnet.
17
If a transformer doubles the voltage, what happens to the current (assuming no energy loss)?
18
What are the two main ways of arranging the coils and the core in a practical transformer?
19
What happens when unlike poles of two magnets are brought close together?
20
What happens when a magnet is heated to a high temperature?
21
What is an electric field?
پاسخ دهید(B)
The region around a charged object where electric force is exerted
22
In the context of electromagnetic induction, what does the rate of change of magnetic flux link to?
23
What type of device uses an electromagnet to open and close a circuit?
24
In a transformer, when the output voltage is greater than the input voltage, it is a:
25
What type of current does a transformer work with?
26
What is the function of a rectifier in a circuit?
27
What type of core increases the strength of an electromagnet?
28
What is the purpose of the split ring commutator in a DC motor?
پاسخ دهید(B)
To reverse the current direction in the coil.
29
What kind of current is necessary for transformers to work?
30
If the current in a coil is reversed, what happens?
پاسخ دهید(B)
The direction of the magnetic field reverses.
31
What is the purpose of laminated sheets in a transformer core?
پاسخ دهید(B)
To reduce heating effects.
32
What type of current is produced by a simple AC generator?
33
What is the difference between hard and soft magnetic materials?
پاسخ دهید(D)
Hard materials retain magnetism.
34
Which method can be used to create a magnet?
پاسخ دهید(B)
Stroking it with a magnet.
35
How does the current in the primary coil relate to the current in the secondary coil of a transformer?
پاسخ دهید(B)
The ratio of the currents is inversely proportional to the turns ratio.
36
Where does the magnetic field come from?
پاسخ دهید(A)
Electric charges in motion
37
How does increasing the current affect the magnetic field strength?
پاسخ دهید(C)
It increases the field strength.
38
How can a piece of steel be turned into a permanent magnet?
پاسخ دهید(B)
Stroking it with another magnet.
39
What does a transformer with a turns ratio of 1:1 do to voltage and current?
40
What is the unit for measuring power?
41
What does a magnetic relay allow?
پاسخ دهید(A)
A small current to control a larger current.
42
In an induction hob, where is the heat produced?
43
What happens to the current in the secondary coil if the number of turns is increased in the secondary coil of a transformer?
44
In the context of generators, what is the main function of a magnetic field?
پاسخ دهید(B)
To facilitate the production of a voltage.
45
Which term describes a material that is attracted to magnets?
46
What does a rectifier do?
47
What is the relationship between the input and output power of an ideal transformer?
پاسخ دهید(C)
Output power equals input power (ignoring losses).
48
پاسخ دهید(A)
The induced current opposes the change causing it.
49
In a transformer, the power output is ideally equal to:
50
What is the purpose of a circuit breaker in a circuit?
پاسخ دهید(C)
To prevent too much current.
