JEE Advanced2006PhysicsCurrent ElectricityActual
Two bars of radius ' r ' and ' 2 r ' are kept in contact as shown. An electric current I is passed through the bars. Which one of the following is correct?
Options
- AHeat produced in bar B C is 4 times the heat produced in bar A B
- BElectric field in both halves is equal
- CCurrent density across A B is doubled that of across B C
- DPotential difference across A B is 4 times that of across B C
Correct answer
A. Heat produced in bar B C is 4 times the heat produced in bar A B
Step-by-step solution
Current flowing through both the bars is equal. Now, the heat produced is given by aligned H & =I^2 R t or H R or H_ A B H_ B C = R_ A B R_ B C & = ( 1 2 r )^2 ( 1 r )^2 & = 1 4 or H_ B C =4 H_ A B aligned ( as R 1 A 1 r^2 )