Question

Statement I: If we double the number of turns of a solenoid, then the magnetic field along the axis of the solenoid increases.
Statement II: At the centre of the loop the magnetic field appears as straight line.

• A. Statement I is true and statement II is false.
• B. Statement I is false and statement II is true.
• C. Both the statement are true.
• D. Both the statements are false.

Answer 1

The correct option is C Both the statement are true.

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 which is 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, the magnetic field at the axis is the sum of magnetic fields from each loop of the coil. Hence, it is n times the magnetic field due to a single loop, since the radii are the same. Now if we take a solenoid with 2n turns, then the magnetic field will be double the previous value. Hence, the magnetic field will increase.

Therefore, both the statements are true.