PhysicsChapter 7: Current Electricity
A.C. and D.C.
Introduction
This topic compares alternating current and direct current.
Definition
D.c.
Direction → one direction. Common sources → cells, batteries, solar cells. Typical use → electronics and battery-powered systems.
A.c.
Direction → reverses periodically. Common source → electrical generators and mains supply. Typical use → electrical power transmission and distribution.
Comparison
Direction D.c. → fixed overall direction. A.c. → reverses. **Waveform Ideal constant d.c. → horizontal line. Sinusoidal a.c. → alternating positive and negative values. Transformers** A.c. can be conveniently stepped up or down using transformers. Steady d.c. cannot be transformed by an ordinary transformer without first being switched or converted.
Why Both Are Used
A.c. is highly convenient for large-scale power distribution. D.c. is widely used by electronic devices, batteries, and many low-voltage systems. Modern electrical systems often convert between the two.
Exam preparation
Exam Focus
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.A.C. and D.C.
Sticky Notes · Quick Revision
D.C.
- One way
A.C.
- Reverses
BATTERY
- D.c.
MAINS
- A.c.
60-second revision
- D.c. → one direction.
- A.c. → reverses.
- Battery → d.c.
- Mains → generally a.c.
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