7.1 Permanent & Induced Magnetism, Magnetic Forces, and Fields

Where is the magnetic field around a magnet the strongest?

Poles

What are magnetic poles?

Region around magnet where magnetic forces are strongest

What happens when two magnets are brought close together?

Exert force on each other

• Two like poles ______ each other.

• Two unlike poles ______ each other.

• Attraction and repulsion between two magnetic poles are examples of a __________ _______.

• repel

• attract

• non-contact force

What is a non-contact force?

Force that acts on objects that are physically separated

What is a permanent magnet?

Magnet that produces its own magnetic field

What is an induced magnet?

Material that becomes magnet when placed inside magnetic field

Permanent magnets can __________ and ________.

• attract

• repel

Induced magnetism always causes a force of ___________.

attraction

What happens when an induced magnet is removed from a magnetic field?

Loses most/all of its magnetism quickly

__________ is the only way to prove that a magnet is a permanent magnet.

Repulsion

What is a magnetic field?

Region around magnet where another magnet or magnetic material experiences a force

What are four magnetic materials?

• Iron

• Steel

• Cobalt

• Nickel

The force between a ________ and a _________ ___________ is always one of attraction.

• magnet

• magnetic material

What does the strength of the magnetic field between a magnet and a magnetic material depend on?

Distance from the magnet.

How can the strength of a magnetic field be determined from a field line diagram?

By the distance between the field lines (density).

• The direction of the magnetic field at any point is given by the direction of the _______ that would act on another ________ pole placed at that point.

• The direction of a magnetic field line is from the ______ (seeking) pole of a magnet to the ______ (seeking) pole of the magnet.

• force

• north

• north

• south

How is the behaviour of a magnetic compass evidence that the core of the Earth must be magnetic?

• A magnetic compass contains a small bar magnet.

• The Earth has a magnetic field.

• The compass needle points in the direction of the Earth’s magnetic field.

Why are the magnetic field lines on a diagram more concentrated at the poles?

That is where the magnetic field is strongest.

How do you plot the magnetic field pattern of a magnet using a compass? (4)

• Place a plotting compass near to a magnet’s north pole

• Mark the direction of the compass’ north pole

• Move it and repeat

• Connect the dots to form a field line

• Figure 6 shows two iron rods placed inside a solenoid.

Explain why the iron rods move apart when the switch is closed. [2 marks]

• Rods become induced magnets

• With the same polarity at each end

Which diagram in Figure 11 shows the direction of the magnetic field between the north pole and the south pole of a magnet? [1 mark]

The magnets are shown in cross-section.

A