I wanna know how you calculate the resistance from A to B!!!?

Question

Don't make me build one of these to check the answers!!!

http://s223.photobucket.com/albums/dd78/floodtl/?action=view¤t=Resistors.jpg

Now look what you made me do:
http://s223.photobucket.com/albums/dd78/floodtl/?action=view¤t=ResistorCheck.jpg

First one to tell me the answer to the second on gets it. I'm an idiot and I need it spelled out for me!!!

Number 2....The trivial one.

Answer 1

Use symmetry.

Assuming all resistors equal, the answer is (3/2)R for 1. 2 is trivial.

OK.

Between points A and B for 2:

at first approximation, the resistance is R. (Two legs of 2R each separate A and B.) But then, upon closer inspection, you find it's (7/8)R.

Answer 2

I believe you don't actually have to set up simultaneous equations, but you instead use the symmetry of the problem. For example, when trying to find the resistance across the whole square, you could imagine a voltage source hooked between them, driving one amp into the whole square. Then by symmetry you know that each of the first legs have one half amp, and so on, working your way through the problem. Then when you're done you could just add up the voltage drops across any path of legs that connect A and B to get the total voltage drop. When I do that I get 1.5 V, so if there's 1. 5 V and 1 A, the resistance must be 1.5 ohms. For the second part of the problem you can do the same thing, or just realize (again by symmetry) that it's half of 1.5 ohms.

Answer 3

You might have to write a set of simultaneous equations and solve for the voltage and current between A and B to get the resistance.

I'm sure that if you look at your textbook you will find they have given you some rules to use in combining resistances.

Answer 4

Electrical resistance?,use ohmmeter.