MAGNETISM AND electromagnetism

Question 1

Basic Summary of magnetism

Answer 1

• South poles attract north poles (and vice versa)
• Some material may become magnetised when placed in a magnetic field
• Iron, steel, nickel, cobalt are magnetic

Question 2

What is the difference between steel and iron’s magnetism?

Answer 2

• Steel - hard magnetic material - retains magnetism
• Iron - soft magnetic material - loses magnetism

Question 3

Define magnetic field line

Answer 3

• The space around a magnet where magnetism can be detected
• Magnetic field line can be seen through use of either plotting compasses or iron filings

Question 4

What are the properties of a uniform magnetic field?

Answer 4

• Field lines are parallel
• Field lines are evenly spaced

Question 5

How may an objects’ magnetism be induced (created)?

Answer 5

• Place a magnetic object e.g. one made from steel or iron into a magnetic field
• Object becomes a magnet (magnetism has been induced)
• The magnetism is temporary as the object loses its magnetism when it’s removed from
  the magnetic field

Question 6

PRACTICAL experiment : INVESTIGATE THE MAGNETIC FIELD PATTERNS OF BAR MAGNETS

Answer 6

1 Place a bar magnet between two books and place a sheet of paper or thin card over it.

2 Sprinkle some iron filings on the paper above the magnet.

3 Tap the paper very gently.

4 The iron filings will move to show the magnetic field pattern.

OR

1 Place a bar magnet on a piece of paper.

2 Place a large number of small compasses on the paper near the magnet.

3 Look carefully at the pattern shown by the needles of the compasses. Repeat the same experiment using two bar magnets, placing them about 5 cm apart.

Question 7

How is a simple electromagnet constructed?

Answer 7

• Connect a wire to a current, add an iron core, wrap wire around a solenoid

Question 8

What is a solenoid?

Answer 8

• Coil of wire

Question 9

How can the magnetic field around a current carrying wire be made stronger?

Answer 9

• Increasing current
• Wrapping the wire into a coil (solenoid)
• Add an iron core

Question 10

How can the magnetic field around a solenoid be made stronger?

Answer 10

• Increasing the number of turns on the solenoid
• Increasing the current

Question 11

Describe the movement of a charged particle in a magnetic field

Answer 11

• The particle will move
• As long as its motion is not parallel to the field

Question 12

Explain why a force is experienced by a wire when a current flows through it

Answer 12

• A current flows through the wire creating a magnetic field around the wire
• This temporary magnetic field interacts with the permanent magnetic field of the bar
  magnets
• A force is created

Question 13

Describe how a motor works

Answer 13

• A current flows through the wire creating a magnetic field around the wire
• this temporary magnetic field interacts with the permanent magnetic field of the bar
  magnets
• A force is created
• The force turns the coil of wire
• A motor has been made

Question 14

How may the motor be made to spin faster?

Answer 14

• Increase the current
• Increase the number of turns of wire
• Increasing the strength of the magnetic field

Question 15

Describe how a loud speaker works

Answer 15

• A current flows through the wire creating a magnetic field around the wire
• This temporary magnetic field interacts with the permanent magnetic field of the bar
  magnets
• A force is created
• The force moves the speaker cone
• This vibrates air particles creating sound waves
• When the direction of the current changes, the direction of the force changes