Page 313 - Basic Electrical Engineering

Figure 3.19 Impedance triangle for R–L circuit

or, Z = R + jX L

Where j indicates rotation by 90° in anti-clockwise direction.

Or, Z cos ϕ = R

and Z sin ϕ = X L

Fig. 3.19 (a) is the same as Fig. 3.19 (b). The current, I has been kept aside

which is common to all the sides. Impedance Z can be represented as the
vector sum of R and X . since IX is leading I by 90° and R is in phase with
L
L
I, we can write