Question

What shape can be drawn through a solenoid to determine the magnitude of its magnetic field?

Answer 1

Answer: Rectangular shape

Explanation: we consider a rectangular shape when we find the magnitude of the magnetic field.

We apply Ampere's circuital law to a rectangular loop.

According to Ampere's circuital law, the magnetic field of a solenoid is directly proportional to the product of the current which is flowing around the solenoid and number of turns per unit line of the solenoid.

`B = \mu n I`

Answer 2

Amperes's law, one of Maxwell's equations, can be used to calculate the magnitude of the magnetic field in different situations. The law states that the integral of B (magnetic field) multiplied by a vector l is equal to the permeability of free space multiplied by the current. In order to use the law, the vector l needs to be drawn about the geometry. For a a solenoid, due to the symmetry, it would make sense to draw a rectangle that has one long side going through the solenoid and the second long side outside of the solenoid.