Sat April 30, 2011 By: Bhavya Garg

Q. Two wires A & B of the same material and length , have their cross-sectional area in the ratio - 1:4. What should be the ratio of heat produced in these wires, if the voltage applied is the same across?

Expert Reply
Sun May 01, 2011
A/C to Joule's law of heating;
H = I2 Rt = V2 t / R
So, voltage remaining same for two wires, the heat produced is inversely proportional to the resistance of the wire.
Now, R = ? l/a
Therefore, H = V2 t / (? l/a) = V2 at / ? l
Hence, Heat produced in wire A / heat produced in wire B = 1/4
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