Question

A coil is wound as a transformer of rectangular cross-section. If all the linear dimensions of the transformer are increased by a factor 2 and the number of turns per unit length of the coil remain the same, the self inductance increased by a factor of

• A. 16
• B. 12
• C. 8
• D. 4

Answer 1

Answer: (C)

8

Answer 2

Self inductance $L = \mu _ { 0 } N ^ { 2 } A / l = \mu _ { 0 } n ^ { 2 } l A$

Where n is the number of turns per unit length and N is the total number of turns and $N = n l$

In the given question n is same. A is increased 4 times and l is increased 2 times and hence L will be increased 8 times.