22.3 Biot- Savart or Laplace's Law

Figure 4

Consider a small element PQ of a conductor through which current i flows. Let d l be the length of the element. Let A be any point at distance r from the center of the element.

Let the line joining the center 'O' to A make Ðq with PQ.

Then, the intensity of the magnetic field at A due to current i in the element PQ is found (by experiments) to be (in magnitude) proportional to i, d l, sin q , .

The direction of is given by Ampere's rule, which is perpendicular to the plane in the diagram and pointing into the plane.

In vector form, equation (1) can be represented as,

Note: Biot- Savart Law is applicable only if the current is a steady current. This is possible only in closed loops or infinite conductors.

Index

22.1 Oersted's Experiments
22.2 Ampere's Rule
22.3 Biot-Savart or Laplace's Law
22.4 Ampere's Law

Chapter 23