General overview (magnetism and the motor effect)

Like poles…

Repel

Opposite poles…

Attract

What is the difference between an induced and permanent magnet?

Permanent magnets produce their own magnetic fields while induced magnets become magnetic only while placed in a magnetic field

What does the magnetic field around a bar magnet look like?

Current flows from north to south, strongest at the poles of a magnet, become weaker further away from the magnet

What does a uniform magnetic field look like?

Current flows from north to south, magnetic field lines have the same length and are spaced equally so the strength is uniform

How does the concentration of field lines relate to the strength of the field?

The closer the lines are, the stronger the field

How can plotting compasses be used to show the shape and direction of the field of a magnet?

Put the magnet on a piece of paper and draw around it. Draw two dots at each end of the needle of the compass with an arrow on the side which points to the south. Keep moving the compass to one of the dots and redraw. Connect the dots and repeat on other places on the magnet’s poles

How does the behaviour of a magnetic compass relate to evidence that the Earth’s core is magnetic?

A freely suspended magnetic compass will align itself with the earth’s field lines and point north, aligning with the North Pole of earth. However, like poles attract, and since we know that the compass’ North Pole is definitely north, we can conclude that the geographic north pole is the earth’s magnetic south pole, and that the earth’s core is magnetic

How can you show that a current can create a magnetic field when going through a long straight conductor (such as a wire)?

Place the wire through a piece of paper with iron filings on it. Let current flow through the wire and the iron filings will rearrange to outline the magnetic field lines produced

What does the magnetic field of a long straight conductor look like?

Circles perpendicular to the conductor, increasing in radius further away from the wire. Use the right hand rule to find out the direction of field lines

What does the strength of the magnetic field of a long straight conductor depend on?

The size of current, and the distance from the conductor

What is a solenoid?

A coil of wire which creates a strong magnetic field when current is passed through

Describe the magnetic field found inside a solenoid

Strong and uniform

Describe the magnetic field found outside a solenoid and explain why

Weak because the field oppose each other’s direction, so cancel out to create a weaker field outside of the solenoid

What happens to a current-carrying conductor placed near a magnet?

It experiences a force which is equal and opposite to the force felt on a magnet

What causes magnetic forces?

When two poles are near each other, magnetic field lines overlap and they cancel each other out. If the two poles are alike, they repel each other; if the poles are opposite, a uniform field is created and they pull together

What is Fleming’s left hand rule?

How does the force on a conductor in a magnetic field cause a rotation in electric motors?

A coil of wire is placed in a magnetic field. The forces on the two sides perpendicular to the field created by the conductor experience forces in opposite directions, causing a rotational effect