# Equivalent resistance problem.

#### quest271

Joined Apr 1, 2016
23

#### quest271

Joined Apr 1, 2016
23
The second pic is what I did. The reason I have two resistors. One is 8 ohm and one is 6 ohm. The way the problem looks . The image is blurry on the resistor. It kind of looks like a 6 or and 8.

#### MrChips

Joined Oct 2, 2009
24,398
1) Do you know how to calculate the equivalent resistance of two resistors in series?
2) Do you know how to calculate the equivalent resistance of two resistors in parallel?

#### MrChips

Joined Oct 2, 2009
24,398
The second pic is what I did. The reason I have two resistors. One is 8 ohm and one is 6 ohm. The way the problem looks . The image is blurry on the resistor. It kind of looks like a 6 or and 8.
Try it both ways and see if you have an answer that matches one of the options given.

#### quest271

Joined Apr 1, 2016
23
The second pic is what I did. The reason I have two resistors. One is 8 ohm and one is 6 ohm. The way the problem looks . The image is blurry on the resistor. It kind of looks like a 6 or and 8.
I know how to calculate series and parallel.

#### quest271

Joined Apr 1, 2016
23
1) Do you know how to calculate the equivalent resistance of two resistors in series?
2) Do you know how to calculate the equivalent resistance of two resistors in parallel?
I tried it with both the 6 and the 8 ohm. Did not get any of those. I am not sure what I am doing wrong.

#### The Electrician

Joined Oct 9, 2007
2,848
I know how to calculate series and parallel.
But you are calculating the equivalent resistance of resistors in series using the formula for resistors in parallel. It appears that you may be having trouble distinguishing between resistors in parallel and resistors in series.

#### quest271

Joined Apr 1, 2016
23
But you are calculating the equivalent resistance of resistors in series using the formula for resistors in parallel. It appears that you may be having trouble distinguishing between resistors in parallel and resistors in series.
You might be right. I guess I just have to practice more.

#### dcbingaman

Joined Jun 30, 2021
442
There are two resistors that are in series. You need to identify them. You are getting the wrong answer because of them.

MrChips gave a good example:

There are 2 resistors in series please identify them. We can then progress to the next step.
Hint: It would be the resistors that have ALL of the current in the circuit passing through them.

Last edited:

#### quest271

Joined Apr 1, 2016
23
There are two resistors that are in series. You need to identify them. You are getting the wrong answer because of them.

MrChips gave a good example:

There are 2 resistors in series please identify them. We can then progress to the next step.
Thanks guys...

#### quest271

Joined Apr 1, 2016
23
There are two resistors that are in series. You need to identify them. You are getting the wrong answer because of them.

MrChips gave a good example:

There are 2 resistors in series please identify them. We can then progress to the next step.
Hint: It would be the resistors that have ALL of the current in the circuit passing through them.
In mrchips example. Is it r1 and r2 in series?

#### quest271

Joined Apr 1, 2016
23

#### dcbingaman

Joined Jun 30, 2021
442
I am having some trouble with this equivalent resistance problem. It is kind of frustrating. I should know how do theses by now. Maybe some of you can point me in the right direction. Here is the problem. View attachment 247806View attachment 247807
Another thing to consider, I am trying to make sure you have a basic understanding before trying to solve the problem. If R2 is variable what is the minimum resistance the circuit can have and what is the maximum resistance the circuit can have? In one case R2 is shorted and in the other case open.

#### dcbingaman

Joined Jun 30, 2021
442
In mrchips example. Is it r1 and r2 in series?
Imagine current is flowing into the top and through the circuit to the bottom. Current in must be current out. The resistors that are in series will have all of the current going through them. Where does the current 'branch' and has multiple paths? Those would be in parallel.

#### quest271

Joined Apr 1, 2016
23

#### dcbingaman

Joined Jun 30, 2021
442

#### MrChips

Joined Oct 2, 2009
24,398
A resistor in a circuit might have a voltage across it and current flowing through it given by Ohm's Law:
I = V/R

Resistors in series have one thing in common. What is it, current or voltage?
Resistors in parallel have one thing in common. What is it, current or voltage?

• atferrari and dcbingaman