# Determine the equivalent resistance of the circuit

1. Apr 5, 2010

### zelda1850

1. The problem statement, all variables and given/known data

a 3.0 ohm resistor an unkown resistor r and two ammeters a1 and a2 are connected with a 12 volt source ammeter a2 reads a current of 5.0 amperes

1) detemine the equivalent resistance of the circuit
2) caculate the current measure of ammeter a 1
3) caculate the resistance of the unknown resistor r

2. Relevant equations

v= 12 v
a2 = 5.0 a
a1 = ?
r1 = 3.0 ohm
r2 =?

this is a parallel circuit so

do i use v/a to find equivalent resistance?

for current do i use v/r to find a?

and for the resistor is this equation right 1/req = 1/r1 + 1/r2

3. The attempt at a solution

i got 2.4 ohm for the equivalent resistance and 4 a for the current dont know if it right

2. Apr 5, 2010

### willem2

There's no way to answer this without seeing the circuit.

3. Apr 6, 2010

### zelda1850

oh here a picture of the diagram for the problem

4. Apr 6, 2010

### Cyosis

The answers you have so far are correct. What exactly makes you doubt your solution?

5. Apr 6, 2010

### Cilabitaon

You are correct so far, so why not go on to find the resistance of the unknown resistor using the formula you have: $$\frac {1}{R_{eq}} = \frac{1}{R_{1}} + \frac{1}{R_{2}}$$

6. Apr 6, 2010

### zelda1850

ok i got 12 r for the resistor using that equation

7. Apr 6, 2010

### Cilabitaon

Which is correct, apart from the units; the units of resistance are Ohms, $$\Omega$$.