Resistance Parallel

Resistance in Parallel Circuits

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Current in Series

Resistance in Series

Wattage in Series

Voltage in Parallel

Current in Parallel

Resistance in Parallel

Wattage on Parallel

Combination 3 Components

Combination 4 Components

Combination 5 Components

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Unbalanced Load

Series Parallel Home

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Resistance Total is the inverse of the sum of the Reciprocals. 

Phwew! That is a mouth full. But with the help of a calculator, finding resistance total in a parallel circuit is just a matter of key strokes.

Note: The reciprocal key is the 1/x key. What happens when you press that key is that the calculator takes the displayed number and divides it into 1.

Here's how a problem goes. Say you know that the resistance of each of four components in parallel is 4 ohms. So you have 4 ohms, 4 ohms, 4 ohms, and 4 ohms in the circuit connected in parallel.

To find the resistance total on the calculator it is done as follows:

enter the value of the first resistor then press the 1/x key

then press + key

enter the value of the second resistor then press the 1/x key

then press +

enter the value of the third resistance then press the 1/x key

then press +

enter the value of the fourth resistance then press the 1/x key

then press the = key

then press the 1/x key one last time.

The reading in the calculator display will be the resistance total in parallel for these components.

Try it. Notice your answer is 1 ohm.

Tip: When all the resistors have the same value, in this case 4 ohms, then the resistance total will always be the value of any one of the resistors divided by how many there are.

In this case that would be 4 divided by 4 equals 1. Neat, eh?

License exams may have a question about resistance total like this: What is resistance total in a parallel circuit where there are 6 resistors that are 36 ohms each? Easy to do, right? Just 36 divided by 6 is 6. Do it in your head, even.

Oh, and as a rough check, resistance total in a parallel circuit will always be less than the smallest resistor in the circuit. Just a math thing.

HERE is a worksheet where you can practice this concept.

Apply this aspect to a circuit with four components HERE.

NEXT

What about a missing resistor when you know the total?

Here is the concept. You enter the total resistance in the calculator. Then press the 1/x key. Then subtract the reciprocal of each of the resistors you know. When you have entered all the known resistors followed by the 1/x key, then press 1/x one last time. The result will be the value of the missing resistor. Let's do the problem above without knowing the value of the fourth resistor, but knowing the total resistance at the beginning. Here we go. 

On the calculator:

total resistance 1 ohm then press 1/x key

then press - (minus) key

enter 4 ohms then press 1/x key

then press -

enter 4 ohms then press 1/x key

then press -

enter 4 ohms then press 1/x key

then press = key

then press 1/x key one last time to find value of missing resistor which should be 4 ohms.

Got it? Great.

Find practice problems HERE.

Find audio support HERE.

 

 
 

 

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