Last Updated: 1 May 2026Verified for JEE 2027
PhysicsJEE & NEET
Difference Between AC (Alternating Current) and DC (Direct Current)
AC and DC are two types of electrical current. AC periodically reverses direction, while DC flows in one direction. Most household electricity is AC, while batteries provide DC.
AC (Alternating Current) vs DC (Direct Current) — Comparison Table
| Aspect | AC (Alternating Current) | DC (Direct Current) |
|---|---|---|
| Direction | Reverses periodically | Flows in one direction |
| Source | AC generators, power grid | Batteries, solar cells, DC generators |
| Waveform | Sinusoidal | Straight line |
| Frequency | 50 Hz (India) / 60 Hz (US) | 0 Hz (zero frequency) |
| Transmission | Efficient over long distances | Loses energy over long distances |
| Transformer | Can step up/down voltage | Cannot use transformers directly |
| Danger | More dangerous at same voltage | Relatively safer |
Key Points to Remember
AC can be transmitted over long distances with minimal loss using transformers
RMS value of AC = Peak value / √2
Power in AC circuits: P = Vrms × Irms × cos φ
Most electronic devices internally convert AC to DC using rectifiers
Exam Relevance
This topic falls under Current Electricity in Physics for both JEE and NEET. Questions on the difference between ac (alternating current) and dc (direct current) appear frequently in competitive exams, both as direct MCQs and as part of numerical/assertion-reason problems.
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