Voltage from current across impedance

In summary, the conversation discusses the relationship between power (S), voltage (V), and current (I) using the formula S=VI*=ZI^2. The question arises whether V should be calculated as ZI or ZI*. It is mentioned that using V=ZI results in a negative answer, but it is suggested that this may be due to not using the root mean square (rms) value for I. It is also noted that the complex conjugate of a quantity may be used in certain cases, but it is not necessary in this situation.
  • #1
perryben
8
0
So the power is S=VI*=ZI^2.

the question is whether V=ZI* or just ZI. Using V=ZI when I calculate the voltage i get a negative answer.

Thanks!
 
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  • #2
perryben said:
So the power is S=VI*=ZI^2.

the question is whether V=ZI* or just ZI. Using V=ZI when I calculate the voltage i get a negative answer.

Thanks!

Are you using the rms value for I? You'll need that. RMS (root mean square) cannot be negative here. Also, rms current is either greater than or equal to the DC current (mathematics of rms vs. average).
 
  • #3
perryben said:
So the power is S=VI*=ZI^2.

the question is whether V=ZI* or just ZI. Using V=ZI when I calculate the voltage i get a negative answer.

Thanks!

Thread moved from EE to homework help.

Why would V = ZI* ? Once you have the complex Z and I, the complex V should just be the product of those two. There are times that you use the complex conjugate of a quantity, but I wouldn't think you would use it here...
 

What is voltage?

Voltage is a measure of the electric potential difference between two points in an electrical circuit. It is often described as the force that moves electrical charge through a circuit.

What is current?

Current is the flow of electric charge through a circuit. It is measured in amperes (A) and is typically represented by the symbol "I".

What is impedance?

Impedance is a measure of the opposition to the flow of electric current in a circuit. It is represented by the symbol "Z" and is measured in ohms (Ω).

How does current affect voltage?

According to Ohm's Law, voltage (V) is equal to the product of current (I) and impedance (Z). This means that as current increases, voltage also increases, and vice versa.

Why is impedance important?

Impedance is important because it determines the amount of current that can flow through a circuit. It also plays a crucial role in maintaining a stable voltage across a circuit by resisting changes in current.

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