- #1

TomK

- 69

- 14

- Homework Statement:
- Can't do circuit problems with 2+ cells consistently. It works for some questions and doesn't for others. I'm guessing this is because my mistakes in one question end up cancelling each other out. I don't get it.

- Relevant Equations:
- https://www.ocr.org.uk/Images/536433-data-sheet.pdf

I wasn't taught how to do it at A-Level in-detail, because there are no questions that expect you to use them in a circuit problem. They only need you to know what the first and second laws are in words (i.e. conservation of charge and energy).

I tried looking it up on YT, but it's confusing. All I know is this:

1) Choose a direction for current to flow (CW or ACW) - consistent for every loop.

2) Choose a p.d. direction (+ to -, or - to +) - consistent for every loop.

3) current into a junction = current out of same junction.

4) sum of potentials in a closed loop = 0. This doesn't make sense to me, but I use it anyway.

5) If p.d. and current direction are against each other, add emf and component potentials. If p.d. and current direction are in same direction, subtract component potentials from emf.

I don't know what counts as a loop. Does it have to start and end at the same cell, or can a loop not involve a cell at all?

Whenever I have a loop that has a second cell in the way, I check if its p.d. direction opposes that of my starting cell. If it does, I subtract its potential from the emf of the starting cell.

I still can't do this question, though.

The answer is 9.6V, but I can't see why.

I tried looking it up on YT, but it's confusing. All I know is this:

1) Choose a direction for current to flow (CW or ACW) - consistent for every loop.

2) Choose a p.d. direction (+ to -, or - to +) - consistent for every loop.

3) current into a junction = current out of same junction.

4) sum of potentials in a closed loop = 0. This doesn't make sense to me, but I use it anyway.

5) If p.d. and current direction are against each other, add emf and component potentials. If p.d. and current direction are in same direction, subtract component potentials from emf.

I don't know what counts as a loop. Does it have to start and end at the same cell, or can a loop not involve a cell at all?

Whenever I have a loop that has a second cell in the way, I check if its p.d. direction opposes that of my starting cell. If it does, I subtract its potential from the emf of the starting cell.

I still can't do this question, though.

The answer is 9.6V, but I can't see why.