CBSE Class 12 · 2009 · Magnetic Effects of CurrentShort Answer

State Biot-Savart's law. A current

I

flows in a conductor placed perpendicular to the plane of the paper. Indicate the direction of the magnetic field due to a small element

d ℓ

at a point P situated at a distance

r

from the element.

Solution

\textbf{Biot-Savart's law:} the magnetic field due to a current element

I d ℓ

at a point P a distance

r

away is

d B = \frac{μ _{0}}{4 π} \frac{I d ℓ \times r}{r ^{3}}, ∣ d B ∣ = \frac{μ _{0}}{4 π} \frac{I d ℓ sin θ}{r ^{2}},

where

θ

is the angle between

d ℓ

and

r

. The direction of

d B

is perpendicular to the plane containing

d ℓ

and

r

, given by the right-hand screw rule (here, into the plane of the paper at P).

CBSE Class 12 Board · 2009 · Subjective