# Help with electrical current and resistances [closed]

I am working on a physics equation on electrical circuits. I understand it in one direction but I am having issues looking at it backwards. I am given the following:

R1 = R2 = R3 = 1.5 Ω

Calculate the equivalent resistance of the following circuit.

I can find equations when I am looking for the Req but I can't find any to find R1,R2,R3 given Req. If anyone wants to help or explain this it would be appreciated.

## closed as off-topic by CuriousOne, Martin, AccidentalFourierTransform, user36790, Qmechanic♦May 9 '16 at 18:49

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$$R_{eq} =\frac R3$$
$$R = 3R_{eq}$$
when $$R_1=R_2=R_3=R$$

• So the resistances are all equal? Different resistors don't have different resistances? Or is that only when regarding the amps? Also thank you very much for answering. – WJU May 9 '16 at 17:56
• Sorry, I thought your question said they are all equal to 1.5 Ohms. If they are different then it is impossible to find R1, R2, R3 given only Req. You would need some extra information, eg that R1=(1/2)R2=(2/3)R3. – sammy gerbil May 9 '16 at 18:01

$R_1=1.5 \Omega$ , $R_2=1.5\Omega$ and $R_3=1.5\Omega$ gives you $$R_{eq} = \frac1{\frac1{1.5}+\frac1{1.5}+\frac1{1.5}}=\frac12=0.5 \Omega$$

You have to use this formula since the different resistors are parallel circuits.

• I think she is just looking for equivalent resistance. So would it just be 1.5 x 3 = 4.5 Ω per resistor then 13.5Ω overall? Honestly this is starting to confuse me. (not your help, just electrical current in general) – WJU May 9 '16 at 18:05
• From your question: "I can find equations when I am looking for the Req but I can't find any to find R1,R2,R3 given Req." So according to your question, you are looking for a formula for R1,R2,R3 when you know Req. I pointed out that it was impossible, and that you can find it if you know Req, R1, and R2. Maybe you misphrased your question? – wythagoras May 9 '16 at 18:09
• Right from the worksheet it says what I put: Calculate the equivalent resistance of the following circuit. (above image goes here) R1 = R2 = R3 = 1.5 Ω – WJU May 9 '16 at 18:13
• In that case your last sentence is very misleading. I will edit the answer. – wythagoras May 9 '16 at 18:14
• I am very sorry, honestly, I appreciate your help. – WJU May 9 '16 at 18:15