Calculate the equivalent resistance

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Sylvia
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Homework Statement


Circuit schematic with a 12 V battery in series with resistor r at the bottom left; resistors 1.0 Ω and 7.1 Ω on top, 4.5 Ω on the left side, 3.2 Ω in the middle vertical branch, and 5.8 Ω on the bottom right.

Ignore the internal resistance of the battery and assume it is merely a battery. Calculate the equivalent resistance of the circuit.

Homework Equations


1/Req = 1/R + 1/R ... (parallel)
Req = R + R ... (series)

The Attempt at a Solution


I know this is fairly simple but I don't understand how you would calculate the equivalent resistance for the three resistors (3.2 ohms, 7.1 ohms, 5.8 ohms). I assumed they were in series and simply added them, and then added 1.0 ohms and 4.5 ohms to get the total resistance. I think this is wrong, can someone explain how you would go about calculating the Req?
 
Sylvia said:

Homework Statement


Circuit schematic with resistors of 1.0 Ω, 4.5 Ω, 3.2 Ω, 7.1 Ω and 5.8 Ω, plus an internal resistance r in series with a 12 V battery at the bottom left.

Ignore the internal resistance of the battery and assume it is merely a battery. Calculate the equivalent resistance of the circuit.

Homework Equations


1/Req = 1/R + 1/R ... (parallel)
Req = R + R ... (series)

The Attempt at a Solution


I know this is fairly simple but I don't understand how you would calculate the equivalent resistance for the three resistors (3.2 ohms, 7.1 ohms, 5.8 ohms). I assumed they were in series and simply added them, and then added 1.0 ohms and 4.5 ohms to get the total resistance. I think this is wrong, can someone explain how you would go about calculating the Req?

I'm afraid you're wrong. All of them aren't in series. See the figure I've uploaded. What can you infer from that? Always deal with 2 resistances at a time. Don't involve 3 together.
 
Attachments
  • Circuit diagram: a 7.1 ohms resistor and a 5.8 ohms resistor joined end to end in a series chain on the left, with an arrow labelled 'Is the same as' pointing to the same two resistors drawn in series on the right.
    resistance.JPG
    7 KB · Views: 660
I see what you are saying, since 7.1 and 5.8 are in series, they must be added together? And then added in parallel to 3.2?
 
Sylvia said:
I see what you are saying, since 7.1 and 5.8 are in series, they must be added together? And then added in parallel to 3.2?
You got that right mate!
 
Sylvia said:
thanks![/QUOT
Glad I could help! :-)