P7 - Magnetism and Electromagnetism

What are the poles of a magnet?

The place where the magnetic forces are strongest

What happens when two magnets are brought close to each other?

They exert a force on each other

What happens when two like poles of magnets are brought close to each other?

The repel each other

What happens when two unlike poles of magnets are brought close to each other?

They attract each other

What type of force is magnetism an example of?

A non-contact force

What is a permanent magnet?

One which produces its own magnetic field

What is an induced magnet?

A material that becomes a magnet when it is placed in a magnetic field

What happens to an induced magnet when it is taken out of a magnetic field?

It loses most/all of its magnetism quickly

What is the only force that is caused by an induced magnet?

A force of attraction

What is a magnetic field?

The region around a magnet where a force acts on another magnet or on a magnetic material

What materials are magnetic?

Iron, cobalt, nickel, steel (an iron alloy)

What type of force exists between a magnet and a magnetic material?

Attractive magnetic force

What does the strength of the magnetic field depend upon?

The distance it is from the magnet. The field is strongest at the poles

How do we define the direction of the magnetic field?

The direction of the magnetic field at any point is given by the direction of the force that would act on another north pole placed at that point

What direction do magnetic field lines point?

From the north seeking pole of a magnet to the south seeking pole of a magnet

How does a magnetic compass work?

It contains a small bar magnet that points in the direction of the Earth's magnetic field

Why does Earth have a magnetic field?

It has an iron core

Draw the magnetic field pattern of a bar magnet.

Image result for magnetic field pattern bar magnet

What happens when a current flows through a conducting wire?

A magnetic field is produced around the wire

What is a solenoid?

A coil of wire

What happens to the magnetic field when a wire is shaped into a solenoid?

It becomes much stronger

Describe the magnetic field inside the solenoid?

It is strong and uniform (it has the same strength and direction at every point)

Describe the shape of the magnetic field around a solenoid?

The same as the shape of a magnetic field around a bar magnet

How can the strength of a solenoid be increased?

By adding an iron core

What is an electromagnet?

A solenoid with an iron core

How can the magnetic field of a solenoid be stopped?

Turn of the current

What is an advantage of using an electromagnetic instead of a permanent magnet?

The magnetic field can be turned on and off

What is the motor effect? (higher tier only)

The term used when a current carrying wire experiences a force, causing it to move, when placed in a magnetic field

Describe what happens when a current carrying wire is put between magnetic poles? (higher tier only)

The magnetic field around the wire interacts with the magnetic field it has been placed in, causing the wire and the magnet to exert a force on each other

To experience the full force from the motor effect, what direction does the wire have to be compared to the magnetic field? (higher tier only)

90o to the magnetic field

When would a wire experience no force from the motor effect? (higher tier only)

If the wire runs parallel to the magnetic field

What does Fleming's left hand rule represent? (higher tier only)

The relative orientation of the directions of the force, the current in the conductor and the magnetic field

What will affect the size of the force acting on the conductor in a magnetic field? (higher tier only)

The magnetic flux density, the size of the current, the length of the conductor that's in the magnetic field

What word equation represents the force exerted on a conductor carrying a current at 90o to a magnetic field? (higher tier only)

Force = magnetic flux density x current x length

What symbol equation represents the force exerted on a conductor carrying a current at 90o to a magnetic field? (higher tier only)

F = B I l

What is the unit and unit symbol of magnetic flux density (B) (higher tier only)

Tesla, T

What is the unit and unit symbol of current (I) (higher tier only)

Amps, A

What happens to a loop of wire carrying a current when placed in a magnetic field? (higher tier only)

It rotates

Why does a loop of wire rotate in a magnetic field? (higher tier only)

The current travels in opposite directions through the magnetic field meaning the forces acting on the wire act in opposite directions

What is used in an electric motor to switch the direction of the current in the wires causing it to continue to rotate? (higher tier only)

A split ring commutator

How do loudspeakers and headphones use the motor effect? (higher tier only)

They convert variations in current in electrical circuits to the pressure variations in sound waves