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Terminal voltage and electromotive force

  • #1
Hi everybody!

I'm a physics-interested guy from Norway, who have a question. We don't have any such exellent forums in Norway. :-) I hope you understand my english by the way. :-)

Homework Statement


We have a battery with internal resistance 2 Ohm. The voltmeter shows 9 volt when no current goes through the circuit (switch open). (Then, the electromotive force is 9 volt, right?)
When this switch is closed, i.e. current goes through the circuit, the voltmeter shows 7,8 volt. In this circuit we therefore have a resistance with 13 ohm.

If we now have two resistances (13 ohm and 30 ohm) switched parallell (do you understand my english. :-) ). (Then we have a resultant resistance 9,07 ohm, right?)

Then the questions:

1. What shows the voltmeter now? (we need to find the terminal voltage, right?)

2. What's the current through the resistance with 13 ohm?



Homework Equations


-


The Attempt at a Solution



1. According to my calculations, the terminal voltage now is 7,4 volt.

2. The current through resistance 13 ohm: 0,567 Ampere.

But I don't know whether this is right?


Hope I'll get answer from some physics genius!! :-)
 

Answers and Replies

  • #2
Dick
Science Advisor
Homework Helper
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I think you've got it. I get SLIGHTLY different answers, but then you are rounding your numbers somewhat differently in different places.
 
  • #3
I think you've got it. I get SLIGHTLY different answers, but then you are rounding your numbers somewhat differently in different places.
Ah!! Good to hear! :-)
To be exact: I calculated the terminal voltage (question 1) to 7,374. Did you get the same answer?
 
  • #4
Dick
Science Advisor
Homework Helper
26,258
618
Ah!! Good to hear! :-)
To be exact: I calculated the terminal voltage (question 1) to 7,374. Did you get the same answer?
No. I got 7.373949579831933. :wink:
 
  • #5
No. I got 7.373949579831933. :wink:
Heh. :-)
Thank you very much by the way!
 

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