Problem 1-13: Voltage of A Current Source


Find voltages across the current sources.
a)
A Current Source Parallel with A Voltage Source
b)
Voltage Across Parallel Elements
c)
Parallel Current and Voltage Sources
d)
Parallel Current and Voltage Sources
e)
Parallel Current and Variable Voltage Sources


Solution

In each case, the current source is parallel with a voltage source. Therefore, the voltage across the current source is equal to the voltage of the voltage source, regardless of other elements.


a)
A Current Source Parallel with A Voltage Source
b)
Voltage Across Parallel Elements

c)
Parallel Current and Voltage Sources

d)
Parallel Current and Voltage Sources
e)
Parallel Current and Variable Voltage Sources

12 thoughts on “Problem 1-13: Voltage of A Current Source

  1. Dr. Li -

    I am trying to understand circuit d better. Why is it that the 6 ohm resister doesn't conduct? What direction does the current flow through the battery? Can it be redrawn in a way making it clearer?

    Thank you.

    1. The $latex 6 \Omega$ is short circuited. Then the all portion of current passes through the wire which is short circuiting the $latex 6 \Omega$. When two sides of a resistor are connected to each other, the voltage across the resistor is zero. Therefore, the Ohm's law also implies that the current is zero: $V=RI=0 \to I=0 $.
      The current of $latex 3 \Omega$ is $latex \frac{3V}{3 \Omega}=1 A $ from the top to the bottom. The current of the current source is $latex 2 A$ from the top to the bottom. So, the current of the voltage source is $latex 2 A + 1 A $ from bottom to the top, i.e. from the negative terminal to the positive one.

  2. thanks alot for sharing your knowledge with us....
    do me a favor?
    what is meant by
    1) voltage controlled current source and
    2) current controlled voltage source ,
    3)voltage controlled voltage source and also
    4) current controlled current source?

    1. sir i want clarity among the four sources.
      1) voltage controlled current source and
      2) current controlled voltage source
      3)voltage controlled voltage source and
      4) current controlled current source.

  3. in these given circuit howcan we find which source is supplying and which source is obsorbing or both are suppling power

  4. thanks alot for sharing your knowledge with us....
    do me a favor?
    what is meant by
    1) voltage controlled current source and
    2) current controlled voltage source ,
    3)voltage controlled voltage source and also
    4) current controlled current source?

    1. 1) voltage controlled current source
      It is a current source whose current is related to a voltage drop somewhere. For example:
      voltage controlled current source
      The current source at right side bottom is a voltage controlled current source. So, it is a current source but instead of having a constant current value, it is current is always two times of the voltage drop across the 2\Omega at top left (2 V_y).

      A very similar definition for the other three sources. Let me know if you need more explanations.

    1. Yes, it can. Like independent current sources, voltage across dependent current sources can be any value. If you connect two nodes of a dependent current source, the voltage across it is zero.

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