Ac current

Definition

AC current, or alternating current, is an electric current that reverses direction periodically. It is commonly used in power supply systems due to its efficient transmission over long distances.

5 Must Know Facts For Your Next Test

1. The frequency of AC current in most household systems is 60 Hz in the United States and 50 Hz in many other countries.
2. AC current can be described mathematically by the equation $I(t) = I_0 \sin(\omega t)$ where $I_0$ is the peak current and $\omega$ is the angular frequency.
3. Root Mean Square (RMS) value of AC current is given by $I_{\text{rms}} = \frac{I_0}{\sqrt{2}}$, which represents the effective value of AC current.
4. Transformers can only operate with AC currents, making it possible to change voltage levels and improve efficiency during transmission.
5. AC circuits may contain resistive (R), inductive (L), and capacitive (C) components, each affecting the phase relationship between voltage and current.

Review Questions

• What is the typical frequency of AC current used in household electrical systems in the United States?
• How do you calculate the RMS value of an AC current given its peak value?
• Why are transformers unable to operate with DC currents?

Related terms

Frequency:

The number of cycles per second in an alternating current, measured in Hertz (Hz).

Transformer:

A device that changes the voltage level of an alternating current using electromagnetic induction.

Impedance:

The total opposition a circuit presents to alternating current, combining resistance, inductive reactance, and capacitive reactance.