Develop an equation for the power consumed by an R-L series circuit. Draw the waveforms of voltage, current, and power.

4.A] Develop an equation for the power consumed by an R-L series circuit. Draw the waveforms of voltage, current, and power.

Answer:-

Circuit draws a current I then there are two voltage drops,
a) Drop across pure resistance, V_R = I _R

b) Drop across pure inductance, V_L = I _XL where X_L = 2 π f L

I= r.m.s. value of current drawn
V_R,V_L= r.m.s. values of voltage drops

The Kirchhoff’s law can be applied to the a.c. circuit but only the point to remember is the
addition of voltages should be vector addition.
Therefore V̅= V̅_R+ V̅_L

Therefore V̅= I̅_R + I̅_XL

Let us draw the phasor diagram for the above case