Voltage and current calculation on a mixed circuit

  • Thread starter sylvarant
  • Start date
  • #1
5
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Homework Statement


I have the following circuit
http://informatici.vankeer.eu/files/2/Untitled.png

R1 = 22 ohm, R2 = 39, R3 = 82, R4 = 100,R5 = 10
and V = 2volt

I'm asked to calculate the voltage and current over de resistors

when the switch is open and when the switch is closed

Homework Equations


when 2 resistors form a combination the current is the same and V = IR

when 2 resistors are in parallell there voltages are the same and Ii = V/Ri


The Attempt at a Solution


well when the switch is open I obtain the following
the resistors R1 and R4 form a combination and so do R2 and R3 the voltage remains equal for both combinations so we can easily calculate the current
I1=I4 = 2v/(22+100)ohm = 0.016 A
now we find the voltage over both resistors
V1= 0.016 * 22 = 0.361 Volt
v4 = 0.016 * 100
Same way for I2 and I3

But I'm stuck when the switch is closed how do I calculate the current and voltage then ?
 

Answers and Replies

  • #2
ptr
28
0
It might be well to read up on "Delta-Wye" transformations.
 
  • #3
berkeman
Mentor
61,259
11,767
But I'm stuck when the switch is closed how do I calculate the current and voltage then ?


Have you learned how to write KCL equations yet? Write the two KCL equations for the left and right nodes, and solve for the two unknowns V(left node) and V(right node).
 

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