# Physics Olympiad question resistance and Electric circuit

1. Nov 12, 2015

### Hashiramasenju

1. The problem statement, all variables and given/known data
In the fig all resistors have resistance R. If pd of V is applied across AB.

1)What is the outcome of joining C and D
2)Whats is the pd across CO
3)what is the resistance across A and B
4)What is the resistance across AO
2. Relevant equations
V=IR
1/∑R=1/R1 +1/R2

3. The attempt at a solution
So for
1) i thought that it would cause a short circuit because instead of flowing through the resistors co &od it would directly flow.
2)?
3)?
4)?

2. Nov 12, 2015

### Staff: Mentor

What would flow from where to where? You are connecting C and D, not E and F.

3. Nov 12, 2015

### donpacino

what is the potential difference between C and D

4. Nov 12, 2015

### Hashiramasenju

zero

5. Nov 12, 2015

### Hashiramasenju

So i understand that between C and D no current flows. So there is ans for 2)no change right ?

6. Nov 12, 2015

### donpacino

yup :)

7. Nov 12, 2015

### Hashiramasenju

so is the current direction i marked correct ? and does current flow from o to d or d to o ?

8. Nov 12, 2015

### donpacino

you wont know unless you know the resistor values... the real question, does the current direction you pick matter?

9. Nov 13, 2015

### Staff: Mentor

As currents can be negative, you can draw the arrows in any direction you like. One direction will lead to positive current, one to negative current - unless the current is zero of course.
Correct. How did you figure that out? A proper description will help with the next part.