# Voltage between two points in circuit

Calculate the voltage between terminals a and b.

I am confused about a problem. I've tried to solve this using the second Kirchoff's rule, but my solution is equal to 0. What am doing wrong?
E=5V R1=600Ω R2=400Ω

My calculations was:
U=R*I
I=5V/1000Ω=0,005A
U=-R1*I+E-R2*I
U=-600*0,005+5-400*0,005=-3+5-2=0[V]

What is wrong?

• I've added the homework-and-exercises tag. In the future, please use this tag for this type of question. Also, please mark up your math using mathjax.
– user4552
Jan 29 '19 at 20:01
• You get zero because the voktages along a closed loop must add to zero. The desired voltage is hidden in your final calculation. Jan 29 '19 at 20:05

## 1 Answer

According to Kirchoff's voltage law, the sum of the potential drops and rises in a circuit is equal to zero.

$$E -iR_1-iR_2=0$$

$$U=E-iR_1$$ $$=iR_2$$

where $$U$$ is the potential difference across resistor $$R_2$$.

For an intuitive basis, think that the charge gets an energy $$V$$ when it passes through the battery, and it dissipates that when it goes through the resistors. By the end of the journey, it's energy is zero. That's what the rule kind of states.