- #1

- 25

- 0

## Homework Statement

I've attached the diagrams for both questions

**Question 24**

Determine the terminal voltage of each battery

**Question 25**

a) What is the potential difference between points a and d

b) What is the terminal voltage of each battery?

## Homework Equations

V = E - Ir

## The Attempt at a Solution

I was able to solve Q24 and Q25 but only after seeing the answer and changing the signs of my equations so I'm just wondering why this is the case:

Q24:

I drew the current is in a clockwise direction

-I(1.0) + 18V - I(6.6) - 12 - I(2.0) = 0

I = 0.625A

For the 18V battery: V = 18 - (0.625 * 1.0) = 17.4V

For the 12 V battery: V = 12

**+**(0.625 * 2.0) = 13.3V

--> The explanation for why the 12V battery is E + Ir is because there is a voltage gain going across the internal resistance from left to right....which I understand

But for Q25:

From an earlier example, I1 = -0.858A; I2 = 2.58A; I3 = 1.73A

a) potential difference Vad = Vd - Va = -I1(30) = -25.7V --> how come you don't use the negative value of current 1, since that was what I calculated from the previous example?

b) 80V battery: the terminal voltage is the potential difference from point g to e

45 V battery: the terminal voltage is the potential difference from point d to b

V(80) = E1 - (I2)r = 80 - (2.58 * 1.0) = 77.4V

V(45) = E2 - (I3)r = 45 - (1.73 * 1.0) = 43.3V

So in this case, how come V(45) is not also E2 + (I3)r? Is it because it is going in the same direction as the current (I3) and in the previous question, it is going against the current?