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Direct current and alternating current sheet
3-mark answer frame

Distinguish between direct current and alternating current. What is the frequency of AC in India, and what is one advantage of AC over DC?

How to lay out the answer. Follow the frame, then write it in your own words.

  1. 1 · Define DC. Current that flows in one direction only; it comes from cells and batteries.
  2. 2 · Define AC. Current that reverses its direction at regular intervals; it is supplied by power stations.
  3. 3 · Give the frequency. 50 Hz in India, so AC changes direction every 1/100 second.
  4. 4 · State the advantage. AC can be sent over long distances without much loss of energy.
  5. 5 · Real life. Home sockets give AC; a phone charger turns it into DC for the battery.
  6. 6 · Close in one line. DC keeps one direction; AC keeps reversing, which suits long-distance supply.

Scoring tip: A two-column table (DC and AC) with three rows scores full marks quickly.