Question

Read the extract given below and answer the question that follows:

The trees inside are moving out into the forest,

the forest that was empty all these days

where no bird could sit

no insect hide

no sun bury its feet in shadow

the forest that was empty all these nights

will be full of trees by morning.

All these days, the forest referred to here was _________ .

(i) filled
(ii) empty

(iii) hidden

(iv) separated

Answer 1

An electromagnet is simply a coil of wire. It is usually wound around an iron core. However, it could be wound around an air core, in which case it is called a solenoid. When connected to a current source, the electromagnet becomes energized, creating a magnetic field just like a permanent magnet. The magnetic flux density is proportional to the magnitude of the current flowing in the wire of the electromagnet.
Advantages of electromagnet over permanent magnets:

• Electromagnets can be designed to produce particular fields and has a possibility of changing the magnetic field over a period of time. This can be achieved by simply changing the current supplied to the coil, allowing the electromagnet to be switched on and off.
• The strength of an electromagnet can be adjusted by the amount of electric current allowed to flow into it. As a result, the same electromagnet can be adjusted for different strength levels.
• If a permanent magnet loses its magnetic properties, as it does by heating to a (maximum) temperature, it will be rendered useless and its magnetic properties can be only recovered by re-magnetizing. Contrarily, an electromagnet loses its magnetic power every time an electric current is removed and becomes magnetic once again when the electric field is introduced.