Units 16 and 17: Magnetism and Static Electricity

We all know that like poles repel and opposite poles attract. You should also know that the magnetic field direction is from north to south.

Remember the definition on magnetic field which will appear on tests: The region around a magnet where a force acts on another magnet or on a magnetic material (such as iron, steel, cobalt and nickel)

The closer the field lines are together, the stronger the magnetic field.

You will most likely have to draw magnetic fields in your exam.

Some metals can be magnetised when , they are called magnetic material.

Materials can be magnetised using electromagnetism or when near a magnetic field.

Steel is a permanent magnet, meaning it is difficult to magnetise and demagnetise.

Soft iron is easy to magnetise and demagnetise.

An electromagnet, or a solenoid, is a temporary magnet magnetised using electricity.

A use of electromagnet that appears in the syllabus is the electric bell. Memorise how it works.

The strength of an electromagnet can be increased by increasing the number of turns in the coil, increasing the strength of current, and vice versa. You can also write "use soft iron core"

Advantages of electromagnet: strength can be changed, can be turned on and off, can be reversed.

Static electricity

An electric field is very similar to a magnetic field.

It can be defined as: The region around a charged object where a force acts on another charge

In this case, opposite charges still attract and the field direction is from positive to negative.

Static electricity can be generated by friction. electrons are transferred, inducing a charge on both objects.

It can also be induced without touching.

the negative charges in the balloon attract the positive charges in the water.

Keep in mind that most of these charged materials are insulators, because conductors cannot hold a charge for long as they conduct the charge away.

That's it for now. It is important to note that I have omitted certain details to make this as concise and helpful as possible. If there is something I have not covered here, please leave a comment on the forums.