An electromagnet is strong enough to lift 200 kg of mass. If you double the number of turns of wire around the core and triple the current, how much will it be able to lift?

1200 kg

Explanation:

Given

Electromagnet can lift a mass of  

Magnetic force necessary to hold mass is proportional to Magnetic field

and magnetic field (B) is proportional to NIA

where N=no of turns

I=current in the magnet

A=area of cross-section

When we double the no of turns and triple the current then

N becomes 2 N

I becomes 3 I

therefore magnetic field becomes 6 times

Thus magnetic force becomes 6 times and we can say that electromagnet can hold the 6 times of given weight

i.e.

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the correct choice is a .

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