KVPY SA Exam 19-Nov-2017 Question Paper

Question : 19 of 80

Marks: +1, -0

A uniform metallic wire of lenght L is mounted in two configurations. In configuration I (triangle), it is an equilateral triangle and a voltage V is applied to corners A and B. In configuration 2 (circle), it is bent in the form of a circle, and the potential v is applied at diameterically opposite points P and Q. The ratio of the power dissipated in configuration 1 to configuration 2 is.

$2/3$
$9/8$
$5/4$
$7/8$

Validate

Solution:

R ={ρl}/ A

(R _1={ρl/3}/ A)

1/R_\eq⇒1/{2R_1}+1/R_1⇒2

R_\eq={2R_1}/3={2ρl/3}/{3A}

i_1 =V/R_\eq=V/{2el}9A

R_\eq⇒R/2⇒1/2({ρl\/2}/A)

i_2 =V/R_\eq⇒V/ {ρl}4A

i_1/i_2=9/8

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