Page 157 - Basic Electrical Engineering
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The open circuit voltage, V OC across the terminals A and B by removing the
resistance R is calculated as
Figure 2.52
Voltage drop across the 30 Ω resistor = 30 × 1 = 30 V. The potential of point
P with respect to N is + 30 V. The potential of point A with respect of point P
is +50 volts. Therefore, the to potential of point A with respect to point N is
+30 +50 = +80 V.
Voltage drop across the 60 Ω resistor in the right-hand-side loop is
calculated as
Potential of point B with respect to point N is + 60 V and that of A w.r.t. N =
30I + 50 = +80V.
1
Now we observe that the potential of point A with respect to point N is +80
V and the potential of point B with respect to point N is +60 V. Therefore,
the potential of point A with respect to point B, i.e., V OC becomes +20 V,
point A being at higher a potential than point B.
To calculate R we redraw the circuit by short circuiting the sources of
eq
EMFs as in Fig. 2.53.
