Question

Two metallic wires A and B are made using copper .The raduis of wire A is r while its length is l.A dc voltage Vis applied across the wire A causing power dissipation ,P.the raduis of B is 2r and its length is 2l and the same dc voltage V IS appilled across is it causing power dissipation P1.

Answer 1

Answer:

Explanation:

Metallic wires = A and B

Radius = r Length = l

Resistance of A = l/πr²

Resistance of B = 2l/π(2r)²

= 2l/4πr²

Resistance in parallel

1/R = 1/(l/πr²) + 1/(2l/4πr²)

1/R = πr²/l + 4πr²/2l

1/R = πr²/l + 2πr²/l

1/R = 3πr²/l

R = l/3πr²

Resistance A = A parallel combination resistance

= l/πr² ÷ l/3πr²

= l/πr² x 3πr²/l

= 3/1

Thus the ratio is 3 : 1 .