Finding the current

  • Thread starter kaspis245
  • Start date
  • #1
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Homework Statement


There is a circuit which is shown in the picture. ##R_1=10 Ω;## ##R_2=10 Ω;## ##R_3=30 Ω##.
I need to find what ampermeter is showing.
123.png


Homework Equations


U=IR

The Attempt at a Solution


1234.png

I am trying to use kirchhoff rules here.

##I_1=I_2+I_3##
##I_1R_1+I_3R_3=80##
##I_2R_2=I_3R_3##

I get that ##I_3=1.14A##. Is this correct?
 

Answers and Replies

  • #2
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Assuming C & D are open as shown, I2 should be 0.
 
  • #3
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But how do I know whether there is voltage between C and D? It is not stated in the problem. In fact, the next question of this problem asks to find the voltage between C & D.
 
  • #4
NascentOxygen
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There will be a voltage between C and D, even though I2 = 0.
 
  • #5
CWatters
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I am trying to use kirchhoff rules here.
snip
I2R2=I3R3

That last line isn't correct. The voltage across R2 and R3 are not the same.

There is nothing connected to C and D so no current flows into or out of C and D. So I2 = 0. Think what that means for I1 and I3.
 

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