Question

• Assertion : When the observation point lies
alona the length of the
current element magnetic field
Reason:
Magnetic field close to
current element is zero
zero.

,​

Answer 1

Answer:

Whole answer is right

Explanation:

But reason is not true

Answer 2

The assertion is true but the reason is false.

When the observation point lies along the length of the current element, the magnetic field is zero.

Because according to Biot-Savart's law field is defined only when the position vector of a point relative to the current element is non zero.

Biot Savart law states that the magnetic field due to a tiny current element at any point is proportional to the length of the current element, the current, the sine of the angle between the current direction and the line joining the current element and the point, and inversely proportional to the square of the distance of that point.

The direction of the magnetic field is in the direction of dl cross r. You can also use the right-hand clasp rule to figure out the direction.