Physics for IGCSE & O level - Magnets And Currents (Section 10)
1
What is the primary function of a step-down transformer?
2
What type of current does a transformer work with?
3
In a magnetic field, what direction does a compass needle align itself?
отговор(A)
Parallel to the field lines.
4
In an ideal transformer, what remains constant (assuming no losses)?
5
What is the effect of moving a magnet near a coil?
отговор(B)
A current is induced in the coil.
6
What are the two key components used in the basic structure of an electromagnet?
7
The changing magnetic field in a transformer core induces a voltage in the:
8
What is the role of slip rings in an a.c. generator?
отговор(C)
To connect the coil to the external circuit.
9
Which of the following is the correct relationship between voltage and current in an ideal transformer?
отговор(B)
Voltage and current are inversely proportional.
10
In what direction does the turning force act on a coil?
отговор(B)
Perpendicular to the magnetic field and current.
11
What does Fleming's Left-Hand Rule help determine?
отговор(C)
The direction of force on a current-carrying wire in a magnetic field.
12
What type of materials are attracted to magnets?
13
What does Lenz's law state?
отговор(B)
The induced current opposes the change that produces it.
14
Which of the following methods can be used to demagnetize a magnet?
15
What happens to the direction of the induced current when the motion of the magnet is reversed?
отговор(A)
The direction of the induced current reverses.
16
What is the rule used to determine the direction of the force on a current-carrying wire in a magnetic field?
17
What does the direction of the induced current depend on?
отговор(C)
The direction of the magnet's movement.
18
What happens to the direction of the induced current if the magnet is pulled out of the coil?
отговор(A)
The direction of the induced current is reversed.
19
What are the key components of a transformer?
20
What is the Earth's magnetic field?
отговор(D)
A magnetic field that acts as if there is a large bar magnet inside the Earth.
21
отговор(C)
Removing the magnetic properties from a magnet.
22
What is a magnetic field?
отговор(A)
The area around a magnet where its force is felt
23
What happens when a current flows through a wire?
отговор(A)
A magnetic field is created around the wire.
24
How is an electromagnet similar to a permanent magnet?
25
What is the effect of placing a piece of iron inside a coil of wire carrying a current?
отговор(C)
The strength of the magnetic field increases.
26
Which of the following would NOT increase the voltage of a generator?
27
In a transformer, the core material is usually made from
28
What type of energy is stored in a magnetic field?
29
How are electromagnets used in hard disk drives?
отговор(B)
To read and write data on the disk
30
If a transformer's turns ratio is 1:4 and the primary voltage is 120V, what is the secondary voltage?
31
Which of the following is the best method to minimize energy loss in a transformer?
32
What will change if the direction of the coil's current is reversed?
отговор(B)
The direction of the turning effect
33
What is the primary function of a transformer?
отговор(B)
To change the voltage of alternating current.
34
Which is a factor affecting the output of a generator?
35
What is the relationship between the input and output power of an ideal transformer?
отговор(C)
Input power equals output power.
36
What is the term used for the creation of a temporary magnet by placing a material, such as iron, within a magnetic field?
37
In a power transmission system, transformers are used to ____ the voltage for transmission.
38
Which of the following is a factor affecting the efficiency of a transformer?
39
How does the magnetic field around a wire change when it carries a larger current?
40
What causes a permanent magnet to have a magnetic field?
отговор(B)
The alignment of the atoms in the material.
41
What is the function of a core in a transformer?
отговор(B)
To provide a path for the magnetic flux.
42
Which of the following correctly describes the relationship between magnetic fields and current-carrying wires?
отговор(B)
Magnetic fields are generated by moving charges.
43
The efficiency of a transformer is primarily reduced by:
отговор(C)
The resistance in the core and the coils
44
How can a magnet be used to produce electricity?
отговор(B)
By moving the magnet relative to a coil of wire.
45
What happens to the magnetic field around a current-carrying wire if the direction of the current is reversed?
отговор(C)
The magnetic field reverses direction.
46
What is the role of the brushes in an electric motor?
отговор(B)
To provide current to the rotating coil.
47
What is the main difference between an A.C. and a D.C. generator?
отговор(B)
A.C. generator uses slip rings, D.C. uses a commutator.
48
When power is transmitted over long distances, a major loss can occur due to
49
How can you increase the force experienced by a current-carrying wire in a magnetic field?
50
What is the primary component used in a loudspeaker that utilizes electromagnetism?
отговор(B)
A permanent magnet and a coil of wire
