Page 276 - Basic Electrical Engineering

change in the coil angle causes a large change in the flux linkage or the
cutting of flux by the conductor is maximum, and hence the induced EMF is
the highest at that position.

3.1.3 Concept of Frequency, Cycle, Time Period, Instantaneous Value,
Average Value, and Maximum Value

One set of positive values and the subsequent one set of negative values of an
alternating quantity constitute a cycle. The time taken for the generation of
one cycle of EMF or flow of current caused due to such an EMF is called the

time period, T. The total number of cycles of EMF or current produced per
second is called the frequency, f. The relationship between time period, T

and frequency, f can be found out as follows:

In T seconds the cycle produced is 1
In 1 second the cycle produced is 1/T

Since f is the cycle produced per second,

f = 1/T (3.2)

The value of an alternating quantity at any instant of time is called its
instantaneous value. Such values are expressed in small lettering like e, i,

etc. For sinusoidal waves, we may write

e = E Sin θ
m
and i = I Sin θ
m
at θ = 0°, e = E Sin 0° = 0
m
at θ = 90°, e = E Sin 90° = E m
m

E is called the maximum value which occurs at θ = 90°, i.e., when the
m
plane of the rotating coil is parallel to the magnetic field.

3.1.4 Sinusoidal and Non-sinusoidal Wave Forms