Factors affecting the strength of an electromagnet

Which of the material is the source of electricity for an electromagnet ?

• Copper wire

• Iron nail

• Battery / AA size cells

• steel clips

As the current in an electromagnet increases the strength of an electromagnet (a)  

How does the number of turns in an electromagnet effects the strength of an electromagnet ?

What happens when the direction of current flowing through the wire connected to the electromagnet changes ?

Which all statements are true in regard to an electromagnet.

• Iron nail or rod increases the magnitude of magnetic field produced by an electromagnet.

• More the current more will be the strength of the magnet.

• Changing the direction of the current changes the polarity of an electromagnet.

• An electromagnet is equivalent to a bar magnet.

Which of the following appliance / instrument uses an electromagnet for its working.

• Automatic door locking

• Television

• mobile phones

• electromagnetic crane