# CBSE Class 12 Physics Chapter 7 Revision Notes

Chapter 7: Alternating Current Revision Notes

- AC stands for
**alternating current**. - It’s a current that
**alternates in magnitude and direction**, and does so on a regular basis.

I = I0 sin ωt or I = I0 cosωt where, I0 = AC’s peak or maximum value.

**Effective Value (rms Value of AC):**It is defined as the AC value over a complete cycle that generates the same amount of heat in a given resistor as steady current in the same resistor at the same time during a complete cycle.

- The effective or rms value of AC is 70.7 percent of the peak value of current.
**AC’s Average or Mean Value:**It is defined as the AC value that would send the same amount of charge through a circuit in half-cycle as steady current would send in the same amount of time.

- The average or mean value of AC is 63.7 percent of the peak value.
- The mean value of AC in a complete cycle will be zero.
**Voltage or alternating emf**It is the emf that alternately and periodically changes in magnitude and direction.

Diagrams are used to represent both AC voltage and AC current, as shown below:

**Inductive Reactance (n.d.)**is a term that refers to (X_{L}) Inductive reactance is the property of an inductor that opposes current flow.

**Capacitive Reactance (X**is the property of a capacitor that opposes the flow of alternating current._{c})

**Wattless Current**, also known as idle current, is the current in an AC circuit when the average power consumption is zero.