Electromagnet Application

Ok b4 we move further to next discussion, i just wanna share with u tis video..its another magical world of magnet..

it is called the magnetic levitation theorem of Earnshaw. Dont worrry, u wont be learning this in SPM.
If u r interested in electrical/electronics engineering course..than u've the chance to dig it deeper..

lets get back to business..the next thing u need to know is
To describe the application of electromagnets such as:
1. Door bell
2. Magnetic Relay circuit
3. Speakers
4. Microphone

All these applications can be asked in paper 2( section A / B / C)., especially in essay section.
U can refer your reference book, or from the electromagnet note , pg 4 as provided in this blog. U must understand how does each device works.