EMI AC

A wire when connected to 220 V mains supply has power dissipation P1. Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is P2. Then P2:P1 is

  1. 1
  2. 2
  3. 3
  4. 4

Answer

P = V2/R and R = ρl/A

Let P1 = V2/R

When the wire is cut down into two pieces, then each wire would have length of l/2 and resistance of R/2.

Equivalent resistance of wire connected in parallel, R2 = R/4 (each wire has resistance R/2)

P2 = V2/R2 = 4P1

The correct option is D.