Calculating Equivalent Resistance

In summary, the problem involves finding the equivalent resistance in a circuit with resistors in parallel and in series. The equivalent resistance of the top part is 27.1 ohms, and the equivalent resistance for the bottom part is also 27.1 ohms. To find the total equivalent resistance, the resistors must be combined in series, taking into account the source between the two loops. Remember to use the formula 1/R1+1/R2+1/Rn=1/Req when combining resistors in parallel.
  • #1
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Homework Statement



In the circuit shown in the figure, R1 = 3.23 Ω, R2 = 5.19 Ω, R3 = 23.1 Ω, and V = 10.7 V.

a) Determine a value for the equivalent resistance.

http://img651.imageshack.us/i/p074figure.png/

Homework Equations



Parallel is 1/R1+1/R2+1/Rn=1/Req
Series R1+R2+R3=Req

The Attempt at a Solution



I know how to calculate the equivalent resistance of the top part and the bottom part, which are the same, but how do you calculate the total resistance with the source between the two? Taking them in parallel is obviously wrong.

The equivalent resistance of the top part is 27.1 ohms if that helps explain it to me.

Thanks
 
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  • #2
Resistors are in parallel if they have the same potential difference, and are in series if they have the same current.

Do either of these cases apply to the equivalent resistors you found for the top and bottom loops?
 
  • #3
When I was putting them in parallel I was forgetting to do the 1/Req. Thanks for the advice, as I got the answer when I went back and tried again.
 

1. What is equivalent resistance?

Equivalent resistance is the total resistance of a circuit or part of a circuit when all resistors are combined into a single resistor. It represents the overall resistance that a current experiences in a circuit.

2. How do you calculate equivalent resistance?

To calculate equivalent resistance, you can use Ohm's Law which states that resistance is equal to voltage divided by current. Additionally, for resistors connected in series, you can simply add their individual resistances. For resistors connected in parallel, you can use the formula 1/R = 1/R1 + 1/R2 + 1/R3 + ... where R is the equivalent resistance and R1, R2, R3, etc. are the individual resistances.

3. Can equivalent resistance be greater than the individual resistances?

Yes, equivalent resistance can be greater than the individual resistances. This is typically seen in circuits with resistors connected in parallel, as the total resistance decreases as more resistors are added in parallel.

4. What is the effect of adding resistors in series vs. parallel?

When resistors are added in series, the equivalent resistance increases as the individual resistances are added together. This results in a higher overall resistance in the circuit. On the other hand, adding resistors in parallel decreases the equivalent resistance as the individual resistances are divided by each other. This results in a lower overall resistance in the circuit.

5. Can the equivalent resistance of a circuit be negative?

No, the equivalent resistance of a circuit cannot be negative. Resistance is a physical property that represents the opposition to current flow, and it cannot have a negative value. If you encounter a negative value when calculating equivalent resistance, it is likely a sign of an error in your calculations.

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