Question

If we double the number of turns per unit length for a solenoid, then the magnetic field along the axis of the solenoid ___________.

• A. will decrease
• B. will increase
• C. cannot be predicted
• D. will remain same

Answer 1

The correct option is B will increase

We can say that, a solenoid is made up of many current carrying circular loops. The magnetic field at the centre of a loop is a straight line due to the sum of the components of magnetic fields at the centre due to different parts of the loop.

When we take a coil having n turns for a given length, the magnetic field at the axis is the sum of magnetic fields from each loop of the coil. Now if we take a solenoid with 2n turns for the same length, then the magnetic field will be double the previous value. Hence, the magnetic field will increase.