Question

Two metallic wire A and B are connected in series.wire A has length l amd radius r while wire B has length 2l and radius 2r.find the ratio of total resistance of series combination and the resistance of wire A if both the wires are of same material .

Answer 1

See the explaination.....hope u understand

Answer 2

Resistance in series is the addition of the equivalent resistances
R= rho* l/a
R(A)= rho*l/πr^2

R(B)= rho*2l /π(2r)^2
= rho*2l/ π*4r^2
R of wires A and B=
rho*l/πr^2+ rho*l/π2r^2
rho*2l/2πr^2+ rho*l/π2r^2
rho(3l/2πr^2)
now ratio =
rho(3l/2πr^2)/rho*l/πr^2
=3/2
or 3:2
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