1.

Resistance of wire having radius r is R. If new wire of radius 2r, is made, then the new resistance of wire= ......

Answer»

`(R)/(2)`
`(R)/(16)`
2R
4R

Solution :`(R)/(16)`
` R = (rho l)/(A) = (rho l A)/(A^(2)) = (rho V)/(pi^(2) r^(4))`
`THEREFORE R PROP (1)/(r^(4))`
`therefore (R_(1))/(R_(2)) = ((r_(1))/(r_(2)) )^(4)`
` (R^(2))/(R)= ((r)/(2r) )^(4)= ((1)/(16))`
`thereforeR_(2) = (R)/(16)`


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