Q.4:- Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be –(a) 1:2 (b) 2:1 (c) 1:4 (d) 4:1
(c) Heat produced in the circuit is inversely proportional to the resistance R.
Let RS be the equivalent resistances of the wires if connected in series and RP be the equivalent resistances of the wires if connected in parallel
Then RS =R+R=2R
And 1/ RP = 1/R +1/R
1/ RP = 2/R
Or RP =R/2
Now the ratio of heat produced is given by