# Current electricity

## Homework Statement

Find the resistance between the A and B( image attached)

## The Attempt at a Solution

I could only simplify the diagram to this (2 attached pic) and i can't proceed any further since i can't identy find any parallel or series circuit/

#### Attachments

Simon Bridge
Homework Helper
You can unfold the first picture ... put points A and B in the corners, then unfold the triangle point A is on so A is outside the big triangle. See how to simplify it now?
No? Imagine a voltage source VAB between A and B and you have to find the total current drawn ... now do you get it?

You end up with the resistors forming an H ...

Last edited:
CWatters
Homework Helper
Gold Member
If you redraw it slightly differently you will see that by symetry one R has no voltage across it. So it can be removed without effecting the circuit. Makes it much easier to simplify further.

You can unfold the first picture ... put points A and B in the corners, then unfold the triangle point A is on so A is outside the big triangle. See how to simplify it now?
No? Imagine a voltage source VAB between A and B and you have to find the total current drawn ... now do you get it?

You end up with the resistors forming an H ...
resistance in between the parallel line of H.......... how do i combine it with others?? (Thanks A LOT for answering! )

resistance in between the parallel line of H.......... how do i combine it with others?? (Thanks A LOT for answering! )

If you see carefully, there's a wheat stone bridge.

Simon Bridge
Homework Helper
Pranav-Arora is correct - it's a Wheatstone bridge. How does one of those work?

You may understand it better if you add a DC voltage source to the diagram between A and B ... one of the resistors in the H does not carry a current: so you can just replace it with an open circuit.

If you still don't see it - use Kirkhoffs rules to find the relationship between VAB and the total current drawn, then Ohm's Law gets you the rest of the way.

sorry-deleting my post

Last edited:
Simon Bridge