Why might an electromagnet be used to pick up old cars in junkyards?

a) electromagnets are inexpensive and easily create revenue.
b) electromagnets are powerful and can be turned on and off easily.
c) electromagnets are easy to operate and can be run by cheap labor.
d) electromagnets are versatile and can pick up any metallic objects in the yard.

Answer;

B) Electromagnets are powerful and can be turned on and off easily.

Explanation;Electromagnets are made by winding a wire through a magnetic material such as soft iron core making a coil, and then passing electric current through the coil thus making the soft iron core magnetic.The strength of the electromagnet depends on the number of coils and also the size of the electric current through the coil.Its advantageous to use electromagnets as compared to using permanent magnets since they are powerful and can be turned on and off easily and also the strength of the electromagnet can be easily adjusted by regulating the amount of current flowing through the coils.

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Ithink the answer would be a