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The resistance of a wire at 20^(@)C is 2...

The resistance of a wire at `20^(@)C` is `20Omega` and at `500^(@)C` is `60Omega`. At which temperature its resistance will be `25Omega`?

A

`50^(@)C`

B

`60^(@)C`

C

`70^(@)`

D

`80^(@)`

Text Solution

Verified by Experts

The correct Answer is:
D
By using  `(R_(1))/(R_(2))`=`((1+at_(1)))/((1+at_(2)))`   `rArr``(20)/(60)`=`(1+20a)/(1+500a)` `rArr` a=`(1)/(220)`
Again by using the same formula for `20Omega` and `25Omega`=`((1+(1)/(220)xx20))/((1+(1)/(220)xxt))`rArr` `t=80^(@)`
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