A wire of length L is used in an electric heater. When the potential
difference across the wire is 200 V, the power dissipated in the wire is
1000 W. The same potential difference is applied across a second similar wire of
length 2L. What is the power dissipated in the second wire?

500 W

Explanation:

Given

When length is L power dissipated is

Potential difference applied is

Resistance of wire is directly proportional to length of wire

Suppose initially Resistance is R

When L changes to

Resistance changes to

Initial Power dissipated is

For 2 R resistance and same voltage, Power dissipated is

So

So