0.23 A across the 20-ohm resistor
Explanation:
The 20-ohm and 35-ohm resistors are in parallel so their combined resistance is
(1/20) + (1/35) = 0.0786 ohm^-1 or 12.73 ohms
These two are in turn connected in series with the 15-ohm resistor so the total resistance of the circuit is
R = 12.73 ohm + 15 ohm
= 27.73 ohm
Hence, the total current drawn by the circuit is
I = V/R = (10 V)/(27.73 ohm)
= 0.36 A
The potential across the 15-ohm resistor is
V1 = IR = (0.36 A)(15 ohm)
= 5.4 V
Now the potential across the 20-ohm and 35-ohm resistors is
V2 = V - V1 = 10V - 5.4V
= 4.6 V
This means that the current across the 20-ohm resistor is
I = V/R = (4.6 V)/(20 ohm)
= 0.23 A
