Question

When a force is applied on a wire of uniform cross-sectional area $3 \times 10 ^ { - 6 } \mathrm {~m} ^ { 2 }$and length 4m, the increase in length is 1 mm. Energy stored in it will be

• A. 6250 J
• B. 0.177 J
• C. 0.075 J
• D. 0.150 J

Answer 1

Answer: (C)

0.075 J

Answer 2

$U = \frac { 1 } { 2 } \times \frac { Y A l ^ { 2 } } { L }$ $= \frac { 1 } { 2 } \times \frac { 2 \times 10 ^ { 11 } \times 3 \times 10 ^ { - 6 } \times \left( 1 \times 10 ^ { - 3 } \right) ^ { 2 } } { 4 }$

$= 0.075 \mathrm {~J}$