Current Electricity and Electrical InstrumentHard

Question

A silver wire of length 10 metre and cross-sectional area 10-8 m2 is suspended vertically and a weight of 10 N is attached to it. Young′s modulus of silver and its resistivity are 7 × 1010 N/m2 and 1.59 × 10-8  Ω-m respectively. The increase in its resistance is equal to (keeping volume constant)

Options

A.0.0455 Ω
B.0.455 Ω
C.0.91 Ω
D.0.091 Ω

Solution

Y =
7 × 1010 =
⇒ x = = m
By volume conservation A1 l1 = A2 l2
10 × 10-8 = A
ᐃR = R − R0 =
ᐃR = −
ᐃR =
= 15.9 × = 0.454 Ω

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