P4.1 - Magnets And Magnetic Fields

Question 1

What is a magnet?

Answer 1

A magnet is any object that has a magnetic field around it.

Question 2

What will magnets do?

Answer 2

A magnet will exert a force on a magnetic material.

Question 3

How many poles do magnets have?

Answer 3

• Magnets have a north pole and a south
  pole.
• Opposite poles attract.
• Same poles repel.

Question 4

How do magnetic field lines move?

Answer 4

Magnetic fields lines go from North to South.

Question 5

How can you tell which magnet is stronger by looking at its field lines?

Answer 5

The denser the magnetic field lines, the stronger the magnetic field and therefore the stronger the magnet.

Question 6

What is a permanent magnet and what can they do?

Answer 6

• A permanent magnet is one which always has a
  magnetic field around it.
• Permanent magnets can attract/repel other
  permanent magnets, but also sometimes non-
  magnets.

Question 7

How can non-magnets be made magnetic?

Answer 7

• The non-magnets have magnetism induced in
  them when the permanent magnet is brought
  close as their domains line up when they are
  bought in a permanent magnetic field.
• A non magnetic material can sometimes be
  temporarily made magnetic and this attract and
  repel other permanent magnets.

Question 8

How does the Earth behave?

Answer 8

The Earth behaves as if there is a huge bar magnet inside it.

Question 9

How is the Earth’s magnetic field?

Answer 9

The Earth’s magnetic field has a north and south pole that exert (small but noticeable) forces upon every magnetic material on Earth.

Question 10

What pole is the geographical south pole?

Answer 10

The geographical south pole is called such because the south pole of magnets point towards it, which means its actually a magnetic north pole (and vice versa).

Question 11

What is a magnetic field?

Answer 11

A region of space within which magnets experience a magnetic force of attraction or repulsion.

Question 12

What is the important sentence in terms of current and wires?

Answer 12

Any time a current flows in a wire, a magnetic field is generated around it.

Question 13

How does a magnetic field exist around a wire?

Answer 13

The magnetic field exists around a wire as concentric rings.

Question 14

Why does the space between the concentric field lines around a wire increase with increasing distance from the wire?

Answer 14

To illustrate the weakening of the magnetic field with distance, just like all fields.

Question 15

What happens if a wire is carrying a greater current?

Answer 15

If the wire is carrying a greater current, the field lines are closer together to illustrate a stronger magnetic field.

Question 16

How can the direction of the magnetic field be worked out?

Answer 16

• Using the corkscrew rule.
• The thumb points in the direction of the current.
  -The fingers wrap around to give the direction of the
  magnetic field lines

Question 17

What is a solenoid?

Answer 17

• A solenoid is a device that acts to increase the
  strength/size of the magnetic field around a
  current carrying wire.
• Solenoids are able to produce magnetic fields
  much stronger than that found in natural magnets.
• Solenoids are used to produce electromagnets.

Question 18

How does a solenoid work?

Answer 18

A wire is looped many times around a piece of metal (not a magnet) that can be magnetised (like iron).

Question 19

What is an electromagnet?

Answer 19

An electromagnet is a magnet which runs on electricity (electric current).

Question 20

How can you change the magnetic field of a solenoid?

Answer 20

An electromagnet’s magnetic field can be switched on and off, by switching the current on and off.

Question 21

How can you increase the strength of the magnetic field in an electromagnet?

Answer 21

• Increase the number of coils in the wire.
• The size of the current through the wire.
• Changing the material of the core inside the coils