Physics 6 - Magnetism and electromagnetism

Question 1

6.2 Describe the force between magnets and magnetic substances

Answer 1

Magnets attract magnetic substances

Question 2

6.3 Describe the properties of magnetically hard and soft materials

Answer 2

Magnetically soft materials lose their magnetism quickly

Magnetically hard materials keep their magnetism permanently

Question 3

6.3 Give the uses of a magnetically hard and magneticallysoft materials

Answer 3

Soft - electromagnets as they can change their magnetic field quickly
Hard - permanent magnets

Question 4

6.4 Define magnetic field and magnetic field lines

Answer 4

Magnetic field - region where magnetic fields feel a force
Field lines - show the size (density of the field lines) and direction (arrows on field lines pointing from North to South)

Question 5

6.5 Sketch the magnetic field between two like poles

Answer 5

JFDI - See Onenote

Question 6

6.5 Sketch the magnetic field between two unlike poles

Answer 6

JFDI - See Onenote

Question 7

6.5 State the elements and compounds where magnetism can be induced and describe how

Answer 7

Induced in iron, cobalt, nickel and steel when they are placed in a magnetic field (domains aligning)

Question 8

6.6 practical: Design an experiment to investigate the magnetic field pattern for a permanent bar magnet

Answer 8

Place the magnet on a flat surface
Place a sheet of paper on top and then sprinkle on iron filings
Shake the paper until they align in field lines
Use a plotting compass to determine the direction of the field line

OR use plotting compasses and draw a line between them

Question 9

6.7 describe how to use two permanent magnets to produce a uniform magnetic field pattern

Answer 9

Place two unlike poles with magnetic fields of similar magnitudes opposite each other.

There is a uniform magnetic field between the two poles

Question 10

6.8 How can a conductor produce a magnetic field?

Answer 10

Pass a current through it

Question 11

6.9P Describe the construction of electromagnets

Answer 11

Wrap an insulated wire around a soft iron nail.

Connect the wires to a power supply. The current though the wires creates an electromagnet

Question 12

6.10P draw magnetic field patterns for the following when each is carrying a current:
a straight wire

Answer 12

JFDI - See one note

If the wire is pointing upwards, the magnetic field is in a circle around it. The field lines get closer together the more central it is

Question 13

6.10P draw magnetic field patterns for the following when each is carrying a current:
a flat circular coil

Answer 13

JFDI - See Onenote

Each of the two wires has a circle of magnetic field lines around it. In the middle, there is one straight line

Question 14

6.10P draw magnetic field patterns for the following when each is carrying a current:
a solenoid

Answer 14

Field lines travel through the coil from N to S and some go around it

Question 15

6.11P Describe the force on a charged particle in a magnetic field

Answer 15

There is a force on a charged particle when it moves in a magnetic field (provided its motion isn’t parallel to the field).

The force is perpendicular to the direction of motion and the direction of the magnetic field.

Question 16

6.12 Explain why a force is exerted on a current-carrying wire in a magnetic field

Answer 16

The magnetic field of the wire interacts with the external magnetic field creating a force

Question 17

6.12 Describe how a d.c. electric motor works

Answer 17

A current is passed through the coil - the magnetic field of that interacts with the external one creating a force - that spins the coil.

Every half turn the split-ring commutator changes the direction of the current around the loop so that it spins in one direction.

Question 18

6.12 Describe how a loudspeaker works

Answer 18

A coil is placed on a permanent magnet, and is wrapped around the base of the cone. An a.c. current is passed through it.

The magnetic field of the coil by the a.c. current interacts with the permanent magnet’s magnetic field creating an alternating force.

The cone vibrates backwards and forwards, creating sound.

Question 19

6.13 A wire carries a current perpendicular to a magnetic field. Describe how to determine the direction of the force on the wire

Answer 19

Use the left hand rule:
First finger - magnetic field (North to South)
Second finger - current (conventional current)
Thumb - motion/thrust (direction of the force)

Question 20

6.14 Describe factors that increase the force on a current-carrying conductor in a magnetic field, such as the coil in a motor or speaker

Answer 20

More current
More turns on the coil
Stronger magnetic field
Soft iron core in the coil

Question 21

6.14 Describe how the direction of the force on a current-carrying conductor in a magnetic field can be changed

Answer 21

Change the direction of the current or the poles of the magnet