Question

Choose the correct option: The magnetic field inside a long straight solenoid-carrying current.

• A. is zero
• B. decreases as we move toward its end
• C. increases as we move toward its end
• D. is the same at all points

Answer 1

The correct option is D

is the same at all points

The explanation for the correct option:

Option(D):

1. A coil of many circular turns of insulated copper wire wrapped closely in a cylinder's shape is generally known as a solenoid.
2. One end of the solenoid basically acts as a magnetic north pole whereas the other acts as a magnetic south pole.
3. The field lines inside the solenoid are known to be parallel and straight.
4. The magnetic field inside a long straight solenoid-carrying current is generally the same at all points inside a magnetic field.
5. The formula for the field inside the solenoid is $B={\mu }_{0}IN/L$ where $B$ is the magnetic field, $N$ is the number of turns in the solenoid, $I$is the current in the coil, $L$ length of the coil.
6. From the above formula, we can say that solenoid is dependent on the number of turns N, length, and magnetic field.
7. The magnetic field inside the long straight solenoid can be shown as:

Explanation for the correct option:

Option(A):

1. The magnetic field inside a long straight solenoid-carrying current is not considered as zero, rather it is generally known to be the same at all points inside a magnetic field.
2. Hence, the given concept is an incorrect one.

Option(B):

1. The magnetic field inside a long straight solenoid-carrying current neither increases nor decreases as we move toward its end.
2. Rather it is said to remain the same at all points inside a magnetic field.
3. Hence, the given option does not correspond to the correct concept.

Option(C):

1. The magnetic field inside a long straight solenoid-carrying current neither increases nor decreases as we move toward its end.
2. Rather it is said to remain the same at all points inside a magnetic field.
3. Hence, the given option does not coincide with the correct concept.

Hence, option d is the correct answer.