Page 53 - Basic Electrical Engineering

Since we have to calculate R , we have to ρ 60
60
ρ = ρ [1 + α (60 − 20)]
20
20
20
−6
−6
= 55 × 10 [1 + 0.0003 × 40] = 55.56 × 10 Ω m
Now,

Current,

1.9 ELECTROMAGNETISM AND ELECTROMAGNETIC INDUCTION

1.9.1 Introduction

Electromagnetism is the study of interaction between electric current and

magnetic field, and forces produced thereof. This section will include
descriptions of magnetic field around current-carrying conductors, magnetic

field produced by a current-carrying coil, force produced on a current-
carrying conductor or a coil when placed in a magnetic field.

A Danish scientist, Oersted in the early nineteenth century discovered that
there was a magnetic field around a current-carrying conductor. Lines of
force in the form of concentric circles existed on a perpendicular plane

around a current-carrying conductor. This meant, magnetism could be created
by electric current. It was also observed that the direction of lines of force got

changed when the direction of current flowing through the conductor was
changed. A few years after the discovery of Oersted, Faraday, another

scientist from England discovered that a magnetic field can create an electric
current in a conductor. When there is a change in flux linkage in a conductor

or a coil, EMF is induced in it. This phenomenon is credited to Faraday who
established famous laws of electromagnetic induction. You will observe that