#### FutureTechn

##### New User

- Location
- cin,oh

- Occupation
- student

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- Thread starter FutureTechn
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- Location
- cin,oh

- Occupation
- student

- Location
- Wisconsin

- Occupation
- Retired Electrical Engineer - Power Systems

What have you tried so far?

Have you tried Ohm's Law?

Have you tried Ohm's Law?

- Location
- Greenville SC

- Occupation
- Retired

Apply those and give us your answer.

- Location
- Wisconsin

- Occupation
- Retired Electrical Engineer - Power Systems

Need answer...

We need your input and participation.

- Location
- Tennessee NEC:2017

- Occupation
- Semi-Retired Electrician

I will give you one hint.

First solve the resistance for two resisters in parallel.

If you have studied that in parallel circuits, that should be easy to solve.

- Location
- Henrico County, VA

- Occupation
- Electrical Contractor

2. We don't like to just answer questions, because you don't learn anything; we like to teach how to answer it yourself.

3. All you need to answer it is Ohm's law and "Watt's law": E = I x R and P = E x I.

4. What voltage would cause what current through 20 ohms to expend 10 watts?

- Location
- San Francisco Bay Area

- Occupation
- Electrical Engineer/ Electrical Testing & Controls

One thing that needs to be clarified is your wording EACH BURNING 10W. When you have 2 resistors in parallel then the 10W power is shared between the two resistors (5W each) because the equivalent circuit value is 10 ohms. Unless you meant that the total circuit wattage is 20W then I stand corrected. Otherwise Ohm's law would not apply.

Yep, the formula P = E squared / R will work to find the voltage.

- Location
- Henrico County, VA

- Occupation
- Electrical Contractor

The values don't alter the formula.Otherwise Ohm's law would not apply.

- Location
- San Francisco Bay Area

- Occupation
- Electrical Engineer/ Electrical Testing & Controls

His definition of power consumption does

- Location
- Wisconsin

- Occupation
- Retired Electrical Engineer - Power Systems

This is clearly a homework problem, so without the 'writers' contribution all we are doing is guessing at the actual problem.

- Location
- Southern Cal

- Occupation
- Electrician NEC 2020

- Location
- NE Nebraska

As worded my first assumption is that the total wattage is 20 watts - 10 ohms per resistor, and that each resistor is 20 ohms. 2 resistors connected in parallel across a voltage source.One thing that needs to be clarified is your wording EACH BURNING 10W. When you have 2 resistors in parallel then the 10W power is shared between the two resistors (5W each) because the equivalent circuit value is 10 ohms. Unless you meant that the total circuit wattage is 20W then I stand corrected. Otherwise Ohm's law would not apply.

Yep, the formula P = E squared / R will work to find the voltage.

This assumes OP did not misunderstand the question and changed critical information when/if it was paraphrased when posted here.

- Location
- Secunda

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- Location
- Ann Arbor, Michigan

- Occupation
- EE

I would reword the question as:

If two 20 ohm resistors are in parallel, and each is dissipating 10w, then what is the voltage across them?

Draw the circuit, look at it closely, and you should easily see how to solve the problem. What is the voltage across a 20 ohm resistor dissipating 10 watts?

.

- Location
- Massachusetts

Parallel circuits, I will assume the voltage across each resistor will be equivalent to to your supply? The current through each one will be different. In a series circuit the voltage over each resistor will differ to the value of resistance and the current will be equal.

The current COULD be different, if they were different resistors in parallel. But current will divide equally between the two paths, if both paths have identical resistance.

- Location
- NE Nebraska

Since they both same Watts and both connected to same voltage then they be the same resistance and each draw same current. (within certain tolerance level anyway)

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- Location
- Secunda

I was meaning in general that in parallel circuits the current will differ in general.Since they both same Watts and both connected to same voltage then they be the same resistance and each draw same current. (within certain tolerance level anyway)

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- Location
- NE Nebraska

True, because resistance is seldom exactly the same. So it depends on what tolerance level is acceptable before you start to consider those differences.I was meaning in general that in parallel circuits the current will differ in general.

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For basic electricity studies for beginners and a question like this you are generally assuming the resistance of both is identical.

For real world problems and solutions, you have to consider how much tolerance can be accepted for the particular application.

- Location
- Springfield, MA, USA

- Occupation
- Electric motor research

Then after everyone laughed about the answer we could have a discussion about significant figures.

-Jon

- Location
- Henrico County, VA

- Occupation
- Electrical Contractor

The voltage is the same as that across a single 20-ohm resistor dissipating 10w.

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