Question

In the circuit in the figure, determine the current in each resistor and the voltage across the 70 ? resistor. (Indicate the direction of the current flow through each resistor through the sign of your answer. Take upward current flow as positive.)

current in 200 ?

current in 80 ?

current in 20 ?

current in 70 ?

voltage across 70 ? resistor:

Answer 1

current in 80,i1 = (+ve) 3A

current in 20,i2 = (-ve) 8A

current in 70,i3 = (+ve) 4A

current in 200,i1+i2+i3 = (-ve)1A

Voltage across 70 resistor = 280V

Answer 2

let Current in

80 Ohm resistor be I1 downwards

20 Ohm resistor be I2 downwards

70 Ohm resistor be I3 downwards

so current in 200 Ohm resistor is I1+I2+I3

Now we have 3 set of voltage balance equations for 3 loops

(I1+I2+I3)*200 + 80*I1 = -40

(I1+I2+I3)*200 + 20*I2 = 360

(I1+I2+I3)*200 + 70*I3 = -80

solving them we get

I1 = -3 Current in 80 Ohm resistor is 3 A upwards

I2 = 8   Current in 20 Ohm resistor is 8 A downwards

I3 = -4   Current in 70 Ohm resistor is 4 A upwards

Current in 20 Ohm resistor is 1 A upwards

V across 70 ohm resistor = 70*I3 = 280 V