Question

How many meters of a thin wire are required to design a solenoid of length 1m and L = 1mH? Assume cross-sectional diameter is very small–

• A. 10 m
• B. 40 m
• C. 70 m
• D. 100 m

Answer 1

Answer: (D)

100 m

Answer 2

Length of the wire l = nl₀2πr and L = µ₀n²l₀πr²

or n =

Thus l =l₀2πr

2πr = $\sqrt { \frac { \mathrm { L } l _ { 0 } 4 \pi } { \mu _ { 0 } } }$

=$\sqrt { \frac { 10 ^ { - 3 } \times 1 \times 4 \pi } { 4 \pi \times 10 ^ { - 7 } } }$= 100 m