Page 308 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 25] DIRECT-CURRENTCIRCUITS 293

Fig. 25-4

SOLVED PROBLEM 25.11
A potential difference of 20 V is applied to the circuit of Fig. 25-4. Find the current through each resistor
and the current through the entire circuit.
Because resistor R 4 has the full 20-V potential difference across it,
V 20 V
I 4 = = = 1.67 A
R 4 12
From Fig. 25-5 we see that the current I 3 also flows through the entire upper branch of the circuit, whose equivalent

resistance is R = 8 . Hence
V 20 V
I 3 = = = 2.5A
R 8
The potential difference V across R 1 and R 2 is

V = V − I 3 R 3 = 20 V − (2.5A)(3 ) = 12.5A

Hence the current I 1 is
V 12.5V
I 1 = = = 1.25 V
R 1 10
and the current I 2 is
V 12.5V
I 2 = = = 1.25 A
R 2 10

Fig. 25-5