Question

A 90 cm long soleniod has six layers of windings of 450 turns each. If the diameter of solenoid is 2.2 cm and current carried is 6 A, then the magnitude of field inside the solenoid, near its centre is

• A. $50 \pi \mathrm { G }$
• B.
• C. $72 \pi \mathrm { G }$
• D. $80 \pi \mathrm { G }$

Answer 1

Answer: (C)

$72 \pi \mathrm { G }$

Answer 2

For six layers of windings the total number of turns

$= 6 \times 450 = 2700$

Now number of turns per unit length

Then the field inside the solenoid near the centre

$\mathrm { B } = \mu _ { 0 } \mathrm { nI } = 4 \pi \times 10 ^ { - 7 } \times 3000 \times 6 = 72 \pi \times 10 ^ { - 4 } \mathrm {~T}$

$= 72 \pi \mathrm { G }$