Magnetism And Electromagnetism

Question 1

What are the two poles of all magnets?

Answer 1

North (or north seeking) and south (or south seeking).

Question 2

What do all magnets produce?

Answer 2

A magnetic field.

Question 3

How can you show a magnetic field?

Answer 3

By drawing magnetic field lines.

Question 4

In which direction do magnetic field lines go?

Answer 4

From north to south.

Question 5

What does the closeness of magnetic field lines indicate?

Answer 5

The strength of the magnetic field; closer lines mean a stronger field.

Question 6

Where is the magnetic field strongest?

Answer 6

At the poles of a magnet.

Question 7

What type of force is always present between a magnet and a magnetic material?

Answer 7

Attractive force.

Question 8

What happens when two like poles are brought near each other?

Answer 8

They repel each other.

Question 9

What happens when two unlike poles are brought near each other?

Answer 9

They attract each other.

Question 10

What does the north pole of a compass point towards?

Answer 10

The south pole of any nearby magnet.

Question 11

What do compasses always point to when not near a magnet?

Answer 11

North.

Question 12

What generates the Earth’s magnetic field?

Answer 12

The core of the Earth must be magnetic.

Question 13

What are the two types of magnets?

Answer 13

Permanent magnets and induced magnets.

Question 14

What do permanent magnets do?

Answer 14

Produce their own magnetic field.

Question 15

What happens to induced magnets when they are brought near a bar magnet?

Answer 15

They turn into a magnet.

Question 16

What is the nature of the force between permanent and induced magnets?

Answer 16

Always attractive.

Question 17

What happens to induced magnets when the magnetic field is removed?

Answer 17

They quickly lose their magnetism.

Question 18

Fill in the blank: Magnets are like ______ - surrounded by fields.

Answer 18

farmers.

Question 19

What basic concept about magnetism is important to learn?

Answer 19

The basics of magnetism take time to understand.

Question 20

What should you do to visualize a magnetic field using a compass?

Answer 20

Move a compass around a magnet and trace its position.

Question 21

What is created around a wire when a current flows through it?

Answer 21

A magnetic field

The magnetic field consists of concentric circles perpendicular to the wire.

Question 22

How can the strength of the magnetic field around a wire be increased?

Answer 22

By wrapping the wire into a coil called a solenoid.

Question 23

What does a compass demonstrate when placed near a current-carrying wire?

Answer 23

The direction of the magnetic field.

Question 24

What happens to the direction of the magnetic field when the direction of the current changes?

Answer 24

The direction of the magnetic field changes.

Question 25

What is the Right-Hand Thumb Rule?

Answer 25

Point your thumb in the direction of current and curl your fingers; the direction of your fingers is the direction of the field.

Question 26

True or False: The strength of the magnetic field changes with the current and the distance from the wire.

Answer 26

True.

Question 27

What happens to the magnetic field inside a solenoid?

Answer 27

It is strong and uniform.

Question 28

What effect does placing an iron core inside a solenoid have?

Answer 28

It increases the field strength and becomes an induced magnet when current flows.

Question 29

What is an electromagnet?

Answer 29

A solenoid with an iron core whose magnetic field can be turned on and off with an electric current.

Question 30

What is the motor effect?

Answer 30

It occurs when a current-carrying wire is placed in a magnetic field, causing the wire to move.

Question 31

What angle must a wire be at to experience the full force in a magnetic field?

Answer 31

90° to the magnetic field.

Question 32

What is the relationship between the force acting on a conductor and the magnetic flux density?

Answer 32

The force increases with the strength of the magnetic field.

Question 33

What formula is used to calculate the force acting on a conductor in a magnetic field?

Answer 33

F = BIl.

Question 34

Fill in the blank: The force acting on a conductor in a magnetic field depends on the magnetic flux density, the size of the ________, and the length of the conductor.

Answer 34

current.

Question 35

What is the unit of magnetic flux density?

Answer 35

Tesla (T).

Question 36

What happens when the current is at 90° to the magnetic field?

Answer 36

The force acting on it can be calculated using F = BIl.

Question 37

If an iron bar of length 0.20 m has a current of 15 A flowing through it in a magnetic field of 0.18 T, what is the force acting on the bar?

Answer 37

0.54 N.

Question 38

What does the term 'magnetic flux density' refer to?

Answer 38

How many field (flux) lines there are in a region.

Question 39

What rule is used to find the direction of the force on a current-carrying conductor in a magnetic field?

Answer 39

Fleming's left-hand rule ## Footnote Fleming's left-hand rule involves using your left hand to determine the direction of the force, magnetic field, and current.

Question 40

In Fleming's left-hand rule, which finger represents the magnetic field?

Answer 40

First finger ## Footnote The first finger points in the direction of the magnetic field.

Question 41

In Fleming's left-hand rule, which finger represents the current?

Answer 41

Second finger ## Footnote The second finger points in the direction of the current.

Question 42

In Fleming's left-hand rule, which part of the hand indicates the direction of motion?

Answer 42

Thumb ## Footnote The thumb points in the direction of the force or motion.

Question 43

What happens to the direction of the force if the current or the magnetic field is reversed?

Answer 43

The direction of the force will also be reversed ## Footnote This principle is crucial for understanding motor operation.

Question 44

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

Answer 44

To swap the contacts every half turn ## Footnote This allows the motor to keep rotating in the same direction.

Question 45

How can the direction of a motor be reversed?

Answer 45

By swapping the polarity of the DC supply or swapping the magnetic poles ## Footnote Reversing the current or the magnetic field changes the direction of rotation.

Question 46

What factors can increase the speed of a motor?

Answer 46

Increasing the current, adding more turns to the coil, increasing the magnetic flux density ## Footnote These factors enhance the motor's performance.

Question 47

Fill in the blank: The forces act on the two side arms of a coil of wire that's carrying a _______.

Answer 47

current ## Footnote The interaction of current with the magnetic field creates forces.

Question 48

True or False: The coil in the motor rotates because the forces act in the same direction on both sides.

Answer 48

False ## Footnote The forces act one up and one down, causing rotation.

Question 49

What is the first step in determining the direction of the coil's rotation using Fleming's left-hand rule?

Answer 49

Draw in current arrows ## Footnote This helps visualize the flow of current in the coil.

Question 50

What does the left-hand rule help students remember during exams?

Answer 50

How to determine the direction of motion in motors ## Footnote It is a useful mnemonic for solving problems related to motor effect.

Question 51

In a motor, what role does the magnetic field play?

Answer 51

It interacts with the current to produce force ## Footnote This interaction is fundamental for motor operation.

Question 52

What is the effect of increasing the current in a motor?

Answer 52

It increases the speed of the motor ## Footnote More current results in stronger magnetic interactions.

Question 53

Fill in the blank: The coil is on a _______ and rotates due to forces acting on it.

Answer 53

spindle ## Footnote The spindle allows for the rotation of the coil.

Question 54

What is the relationship between current direction and force direction in a magnetic field?

Answer 54

They are perpendicular to each other ## Footnote This perpendicular relationship is a key aspect of Fleming's left-hand rule.