Basics of AC and DC

Direct Current (DC)

• Definition: Current that flows in a single direction.
• Source: Batteries, solar cells, DC generators.
• Characteristics:
• Constant magnitude over time
• Polarity (+ and -) remains fixed
• Uses: Most electronics, flashlights, portable devices

Alternating Current (AC)

• Definition: Current that periodically changes direction and magnitude.
• Source: Power grids, AC generators
• Characteristics:
• Represented by a sine wave
• Polarity (+ and -) switches back and forth
• Has frequency (measured in Hertz - Hz)
• Uses: Homes, businesses, long-distance power transmission

Study Notes

• Voltage and Current in AC: In AC circuits, both voltage and current change over time, often following a sinusoidal pattern.
• RMS Value: AC circuits use the root-mean-square (RMS) value, an equivalent DC value that would produce the same heating effect.
• Frequency: The number of times an AC waveform completes a full cycle in one second (measured in Hertz). Common frequencies include 50 Hz and 60 Hz.
• Advantages of AC:
• Easily transformed to higher or lower voltages using transformers.
• More efficient for long-distance transmission due to reduced power loss
• Advantages of DC
• Most electronics function on DC
• Ideal for storing energy (batteries)

Short Notes

• DC: Steady, one-directional flow
• AC: Changing direction, sinusoidal pattern
• AC has frequency (Hz), DC does not
• AC is ideal for power transmission
• DC powers most electronics

Point-Based Notes

• DC flows in one direction, and AC changes direction periodically.
• DC is from batteries, and AC is from the power grid.
• AC voltage is easily changed using transformers.
• AC has a frequency (Hz), and DC has zero frequency.
• AC waveforms are often represented by sine waves.
• RMS value is the DC equivalent of an AC voltage/current.
• AC is good for transmission. DC is good for powering devices.
• Most household appliances use AC power.
• AC motors are used in industrial applications
• DC motors are used in toys and small appliances.

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