Why does OHMs law not work on AC circuits?

In summary, OHMs law does not work on AC circuits because the current and voltage are constantly changing, making it difficult to accurately apply the law. In contrast, DC current flows in one direction, while AC current changes direction periodically. The relationship between current, voltage, and resistance in an AC circuit is not as straightforward as in a DC circuit, as the variables may not always be in phase. While OHMs law can still be used to calculate resistance in an AC circuit, it may not provide an accurate value due to the varying resistance. Other laws, such as Kirchhoff's laws, are more applicable to AC circuits.
  • #1
qlc
3
0
can someone please explain to me physically how is it that
when i have an AC source and i measure Voltage on a resistor its the same with and without the resistor
and when i have a DC source and i measure Voltage again on the resistor and now there's a different reading

its like ohm law doesn't support AC circuits but why ?
 
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  • #2
Did you use the peak value or the r.m.s. value of the AC source for your computation?
 
  • #3
Ohm's law works fine for AC circuits. It sounds like your AC source is closer to ideal.
 

1. Why does OHMs law not work on AC circuits?

OHMs law states that the current flowing through a conductor is directly proportional to the voltage applied, while the resistance remains constant. However, in AC circuits, the current and voltage are constantly changing, making it difficult to apply OHMs law accurately.

2. How does AC current differ from DC current?

In a DC circuit, the current flows in one direction, while in an AC circuit, the current changes direction periodically. This constant change in direction makes it challenging to measure the current and voltage accurately, leading to OHMs law not being applicable.

3. What is the relationship between current, voltage, and resistance in an AC circuit?

The relationship between current, voltage, and resistance in an AC circuit is not as straightforward as in a DC circuit. In an AC circuit, the current and voltage are not always in phase, and the resistance may also change with the frequency of the current. This makes it difficult to apply OHMs law, which assumes a linear relationship between these variables.

4. Can we still use OHMs law to calculate the resistance in an AC circuit?

Yes, we can use OHMs law to calculate the resistance in an AC circuit, but it may not give us an accurate value. This is because OHMs law assumes a constant resistance, which may not be the case in an AC circuit where the resistance may vary with the frequency of the current.

5. Are there any other laws that govern AC circuits?

Yes, there are other laws that govern AC circuits, such as Kirchhoff's laws, which state that the sum of currents entering and leaving a node in a circuit must be zero, and the sum of voltage drops in a closed loop must be equal to the applied voltage. These laws are more applicable to AC circuits than OHMs law.

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