1. Alternating Current (AC)

Concept Explanation:
Alternating Current (AC) is a type of electrical current where the flow of electric charge periodically reverses direction. In contrast to Direct Current (DC), which flows steadily in one direction, AC is characterized by its oscillating nature, making it the standard form of electricity used in homes and businesses.

Key Characteristics of AC:
- Frequency (f): The number of cycles per second, measured in Hertz (Hz). Commonly, the AC frequency is 50 Hz or 60 Hz, depending on the region.
- Amplitude (V₀ or I₀): The maximum value of voltage or current in the AC wave.
- Period (T): The time taken to complete one cycle of AC, inversely related to frequency (T = 1/f).

Mathematical Representation:
The voltage and current in an AC circuit can be expressed as:
V(t) = V₀ sin(ωt)
I(t) = I₀ sin(ωt)
where:
- V(t) is the instantaneous voltage,
- I(t) is the instantaneous current,
- V₀ is the peak voltage,
- I₀ is the peak current,
- ω is the angular frequency (ω = 2πf).

Example Problem:
An AC voltage source has a peak voltage of 170 V and a frequency of 60 Hz. Write the equation for the instantaneous voltage.

Solution:
The angular frequency ω is:
ω = 2πf = 2π × 60 rad/s
The equation for the instantaneous voltage is:
V(t) = 170 sin(120πt)