Question

two wiresof same material having length in the ratio 3:4 are connected in series . the potential difference across them is 12 v and9 v .the ratio of their radii is​

Answer 1

As the conducting wires of the same material and of equal lengths there resistance will be equal, let it be R.

When both are connected in series.

Reqs =R+R =2R ...(i)

When both are connected in parallel.

=

Reqp=R/2...(ii)

Heat is related to resistance by,

H=ReqT

putting value of Req from (i) to find Hs,heat produce in series combination.

Hs=(2R)T..(iii)

putting value of Req from (ii) to find Hp,heat produce in parallel combination.

Hp=(R/2)T...(iv)

Dividing (iii) by (iv)

Hs/Hp=(2R)T/(R/2)T

=4/1

Therefore ratio is 4:1.