Topic 12 Magnetism and the motor effect.

Question 1

What is a magnet?

Answer 1

A magnet is an object that produces a magnetic field and can attract materials like iron, nickel, and cobalt.

Question 2

What are magnetic materials?

Answer 2

Magnetic materials are substances that can be attracted to a magnet, such as iron, nickel, cobalt, and some of their alloys.

Question 3

What is a magnetic field?

Answer 3

A magnetic field is the region around a magnet where magnetic forces can be felt. It is represented by field lines that show the direction of the force.

Question 4

What is the shape of the magnetic field around a bar magnet?

Answer 4

The magnetic field lines around a bar magnet form closed loops, emerging from the north pole and entering the south pole.

Question 5

What do the magnetic field lines represent?

Answer 5

The direction and strength of the magnetic field. Closer lines indicate a stronger field, and the direction shows the force on a north pole.

Question 6

What is the Earth’s magnetic field?

Answer 6

The Earth’s magnetic field is similar to that of a giant bar magnet with a magnetic south pole near the geographic North Pole and a magnetic north pole near the geographic South Pole.

Question 7

What is a uniform magnetic field?

Answer 7

A uniform magnetic field has parallel and evenly spaced field lines, indicating that the field strength is the same at every point.

Question 8

What happens when two like poles of magnets are brought close together?

Answer 8

They repel each other.

Question 9

What happens when two unlike poles of magnets are brought close together?

Answer 9

They attract each other.

Question 10

What is the motor effect?

Answer 10

The motor effect is the force experienced by a current-carrying conductor placed in a magnetic field. This force is strongest when the current is perpendicular to the magnetic field.

Question 11

What is Fleming’s Left-Hand Rule?

Answer 11

Fleming’s Left-Hand Rule helps predict the direction of the force on a current-carrying conductor in a magnetic field.
Thumb: Direction of the Force (motion)
First Finger: Direction of the Magnetic Field
Second Finger: Direction of the Current

Question 12

What factors affect the size of the force in the motor effect?

Answer 12

The size of the current, the strength of the magnetic field, and the length of the conductor in the magnetic field.

Question 13

What is the equation for calculating the force on a current-carrying conductor in a magnetic field?

Answer 13

Force = Magnetic flux density × Current × Length of conductor in the field

Question 14

What is magnetic flux density?

Answer 14

Magnetic flux density is a measure of the strength of a magnetic field, measured in teslas (T).

Question 15

What is an electromagnet?

Answer 15

An electromagnet is a type of magnet where the magnetic field is produced by an electric current. It can be turned on and off.

Question 16

How can the strength of an electromagnet be increased?

Answer 16

By increasing the current, adding more turns to the coil, or using a core made of a magnetic material like iron.

Question 17

What is the principle behind an electric motor?

Answer 17

An electric motor uses the motor effect to convert electrical energy into mechanical energy by creating a rotational force.

Question 18

What is the purpose of the split-ring commutator in a DC motor?

Answer 18

The split-ring commutator reverses the direction of current flow every half-turn, ensuring the motor continues to spin in the same direction.

Question 19

What is the difference between permanent magnets and electromagnets?

Answer 19

Permanent magnets have a constant magnetic field, while electromagnets can be turned on and off and their strength can be adjusted.

Question 20

What are applications of the motor effect?

Answer 20

The motor effect is used in electric motors, loudspeakers, and meters like galvanometers.