AC and DC
AC is alternating current, which changes direction periodically, while DC is direct current, which flows in one direction only.
Practice This ConceptMain explanation
Teacher explanation
In DC, the flow of charge remains in the same direction. A battery gives DC in school-level circuits. In AC, the current changes direction again and again, so its value and direction vary with time. Household mains supply is AC. This difference matters because some devices and transmission systems are designed for one type more than the other.
Example
A torch cell provides DC, while the electricity supplied to homes is AC.
Simple analogy
AC alternates, DC directs one way.
Common confusion
Students often think AC and DC differ only in strength. The key difference is direction and variation with time.
Exam tip
For short answers, clearly state direction change for AC and single direction for DC, then give one example each.
Answer writing and exam use
1-mark use
Write the exact meaning of ac and dc in one clean line.
2-mark use
Define ac and dc and add one example or condition.
3-mark use
Explain ac and dc, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
Open the concept quiz intro first, review the test details, and then start a focused MCQ set from this concept only. Instant score and answer review are live now.
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