Page 291 - Basic Electrical Engineering

If current is leading the voltage by π/2 degrees, we will represent the
current, i as

i = I sin (ωt − π/2)
m

If two voltages v and v are represented as in Fig. 3.8 (c), they can be
B
A
expressed as

This is because voltage v is leading the voltage v . The maximum value
A
B
of v is appearing π/2 degrees before the maximum value of v appears.
A
B
However, if v is taken as the reference voltage we can express v and v as
A
B
B
v = V sin ωt
B
m

v = V sin (ωt − π/2)
A
m

Example 3.1 An alternating voltage of 100 sin 314 t is applied to a half-
wave diode rectifier which is in series with a resistance of 20 Ω. What is the
RMS value of the current drawn from the supply source?

Solution:

Figure 3.9 Circuit diagram of example 3.1

We have,