Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Magnetic Field due to a Circular Coil

Objective

To understand the nature of magnetic field produced by a circular current carrying coil.

Introduction

When a current passes through a circular coil, it produces a magnetic field. The field at the centre of the coil is perpendicular to the plane of the coil. The direction of the field is determined by the right hand rule i.e., if the thumb of the right hand point in the direction of current and the fingers point towards the point where magnetic field direction is required then curling of the fingers gives the direction of magnetic field.

Apparatus

circular coil, magnetic needle, battery

Procedure

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Take enameled copper wire of AWG 18 and wrap about 20-25 turns on a cylindrical object like glass or bottle. The diameter could be about 5 cm. Remove the coil from the cylindrical object and tie it at 3-4 places with the help of cellophane tape or thread. Leave about 10 cm of the wire at each free end of the coil. Fix this coil in vertical position to a flat base such as plastic sheet such that half the coil is inside and other half is outside (see figure). You can use M-seal or any other adhesive to do so. Remove enamel from two free ends of the coil by scratching it with a knife. Paste a white paper on the flat base.

Connect this coil to the DC power supply. Take a magnetic needle and draw the magnetic lines of forces.