Which of the following uses direct current?

Which of the following uses direct current?

• A. Battery-operated watches and devices
• B. Mains electricity
• C. Three-pin plug
• D. Power supplied to a house

Answer: (A)

Direct current flows in one direction, with voltage that stays the same polarity. This is what batteries produce, so devices powered by batteries run on direct current. In contrast, mains electricity is alternating current, where the direction of the current and the polarity of the voltage continually reverse. The three-pin plug and the power supplied to a house are connected to the mains and carry AC. Some devices that run from mains have internal power supplies that convert AC to DC for their circuits, but the supply itself is AC. Therefore, battery-operated watches and devices use direct current directly.

Direct current flows in one direction, with voltage that stays the same polarity. This is what batteries produce, so devices powered by batteries run on direct current. In contrast, mains electricity is alternating current, where the direction of the current and the polarity of the voltage continually reverse. The three-pin plug and the power supplied to a house are connected to the mains and carry AC. Some devices that run from mains have internal power supplies that convert AC to DC for their circuits, but the supply itself is AC. Therefore, battery-operated watches and devices use direct current directly.