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  • Two bars of radius r and 2r are kept in contact as shown. An electric current I is passed through the bars. Which one of following is correct? <img alt="" src="https://cdn.

Two bars of radius r and 2r are kept in contact as shown. An electric current I is passed through the bars. Which one of following is correct?

 

Option: 1

Heat produced in bar BC is 4 times the heat produced in bar AB 
 


Option: 2

Electric field in both halves is equal 


Option: 3

 Current density across AB is double that of across BC 

 


Option: 4

 Potential difference across AB is 4 times that of across BC 


Answers (1)

best_answer

Current flowing through both the bars is equal.

Now, the heat produced is given by

\begin{aligned} \mathrm{H} &\mathrm{ =I^2 R t }\\ \mathrm{H} &\mathrm{ \propto R \text { or } \frac{H_{A B}}{H_{B C}}=\frac{R_{A B}}{R_{B C}} }\\ &\mathrm{ =\frac{(1 / 2 r)^2}{(1 / r)^2} \quad\left(\text { as } R \propto \frac{1}{A} \propto \frac{1}{r^2}\right) }\\ &\mathrm{ =\frac{1}{4} \text { or } H_{B C}=4 H_{A B}}\\ \end{aligned}

 

Posted by

Ritika Kankaria

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