They look like they are in series.

Correct, can you answer why? Is it the current that is the same or the voltage that is the same for all three resistors?

 

It is r1 and r3 but can you explain why?

r1 and r3 is getting all of the current. The current is splitting between r2 and r4.

 

r1 and r3 is getting all of the current. The current is splitting between r2 and r4.

Excellent. Do you want to try to tackle the original problem again? Just identify in the original circuit which are in series and which are in parallel as the first step.

 

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?

In series the current is the same so they have current in common. In parallel they voltage is the same so they have voltage in common.

 

In series the current is the same so they have current in common. In parallel they voltage is the same so they have voltage in common.

Correct.
Hence in the following circuit diagram, which resistors are in series and which resistors are in parallel?
(This is a trick question).

 

Correct.
Hence in the following circuit diagram, which resistors are in series and which resistors are in parallel?
(This is a trick question).

View attachment 247819

To me it look like r1 , r2 and r3 are in series.

 

To me it look like r1 , r2 and r3 are in series.

Is the current through R2 the same as that in R1?
Why is R2 selected instead of R4? Why is R2 any different from R4?

 

Is the current through R2 the same as that in R1?
Why is R2 selected instead of R4? Why is R2 any different from R4?

Technicaly r4 would be in series with r1 and r2.

 

Technicaly r4 would be in series with r1 and r2.

I mean technicaly r4 would be in series with r1 and r3.

 

I mean technicaly r4 would be in series with r1 and r3.

No.

The current through R4 is not the same as the current through R1 and R3.
Similarly, the current through R2 is not the same as the current through R1 and R3.
Hence neither R2 nor R4 are in series with R1 and R3.

Neither R2 nor R4 have any current or voltage common with R1 and R3.
R2 and R4 are not in series or parallel with R1 and R3.

What do R2 and R4 have in common? Is it current or voltage?

 

They look like they are in series.

Correct. I can see where you are going wrong. When you analyze the circuit FIRST identify resistances that are in parallel. Then identify resistance that are in series.

 

To me it look like r1 , r2 and r3 are in series.

Ok, imagine you are an electron and you want to get from the input terminal of this circuit to the output terminal.
Question 1: Do you have a choice in going through R1 or can you take a different path?
Question 2: Do you have a choice in going through R2 or can you take a different path?
Question 3: Do you have a choice in going through R3 or can you take a different path?
Question 4: Do you have a choice in going through R4 or can you take a different path?

 

I mean technicaly r4 would be in series with r1 and r3.

Here is an easier question that I know you know the answer to this. This IS NO DIFFERENT than the circuits we where just looking at:


Ok the lines are roads/highways the boxes are locations. You are at the circle start and want to get to the circle end and you are only allowed to use the highways (lines) I provided.
Questions:
1. Do you have to go through Tucson to get from start to end?
2. Do you have to go through ShowLow to get from start to end?
3. Do you have to go through Pheonix to get form start to end?

If you have to go through a certain city to get to your destination then that city is in series in this 'circuit'
If you have a choice between 2 or more cities, those cities are in parallel to each other.

 

Here is an easier question that I know you know the answer to this. This IS NO DIFFERENT than the circuits we where just looking at:

View attachment 247825
Ok the lines are roads/highways the boxes are locations. You are at the circle start and want to get to the circle end and you are only allowed to use the highways (lines) I provided.
Questions:
1. Do you have to go through Tucson to get from start to end?
2. Do you have to go through ShowLow to get from start to end?
3. Do you have to go through Pheonix to get form start to end?

If you have to go through a certain city to get to your destination then that city is in series in this 'circuit'
If you have a choice between 2 or more cities, those cities are in parallel to each other.

We don't need analogies for this. Let us stick to using resistors, circuit topology and Ohm's Law.

 

We don't need analogies this. Let us stick to using resistors, circuit topology and Ohm's Law.

Probably true. The TS though is struggling with the principle after the original attempts to help explain it. This is why I have turned to an analogy, it could be the inroad that helps the TS. Everyone thinks a little different from each other.