What is the total effective resistance of the two resistors? A 12.4-ohm resistor, R1, and a 30.-ohm resistor, R2, are to be connected in parallel between points A and B in a circuit containing a 90.-volt battery.

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For resistors in parallel, the effective resistance will always be less than the lowest individual resistor in the circuit.

To find the effective resistance (Re) use the following formula:

1/Re = 1/R1 + 1/R2 + ...

In your example:

1/Re = 1/12.4 + 1/30

solving for Re = 8.77...

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For resistors in parallel, the effective resistance will always be less than the lowest individual resistor in the circuit.

To find the effective resistance (Re) use the following formula:

1/Re = 1/R1 + 1/R2 + ...

 

In your example:

1/Re = 1/12.4 + 1/30

solving for Re = 8.77 ohms.

Just remember to take the inverse of your answer on the left to get the value of Re!

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