chapter 16 magnetism and electromagnetism

properties of magnets (6)

Distinguishing magnets and unmagnetised magnetic materials

Induced Magnetism/ induced magnet

** opposite pole will be induced

Ways to magnetised

1. by stroking with a strong magnet

2. place in a current-carrying solenoid

right-hand grip rule

Demagnetisation

temporary and permanent magnets

magnetic field lines

Characteristics of magnetic field lines:

-the magnetic field lines never cross each other

-the magnetic field lines are continuous and they form closed loops

-the distance between the magnetic field lines represents the strength of magnetic field. The closer the lines, the stronger the magnetic field

** the needles of the plotting compasses will point in the direction tangential (touches curve at single pt)l to the magnetic field line

** always enter south and exits north

**always from north to south

Example of magnetic field lines

Example of magnetic field lines

Magnetic field due to current in straight wires:

right-hand grip rule

The directions of the needles on the compasses follow the right-hand grip rule. If we grip the conductor with our thumb pointing in the direction of the conventional current (not electron flow), the curl of the fingers shows the direction of the magnetic field

Magnetic field due to current in solenoid

When will a current in a wire cause the wire to move?

Fleming’s left-hand rule