Question

What is the current through resistor R1? (Please explain, thanks!)

Answer 1

Equivalent resistance of R2 and R3 = 90+120 = 210 Ω

Now let's assume current in resistor R1 = I Towards R2.

That from 9V =i1 from the positive terminal of battery and i3 from R2.

Now potential across R2 and R3 combined = 9V

Thus, i3 = 9/210 =0.0428571429 A

Applying Kirchoffs voltage law in loop containg 9V and 1V battery

we get,

1- I*R1 -9=0

-8/R1 = I = -8/60 =-0.133 A

Hence current through R1 resistor = 0.133 A towards the positive terminal of 1V battery.