Examkin

Question

Difficulty: MediumDirect Current (DC) vs. Alternating Current (AC)

Match each electrical power source or practical application on the left with its corresponding current characteristic and operational principle on the right.

  • High-voltage long-distance electrical utility gridUtilizes alternating current (AC) so voltages can be easily stepped up or down with transformers to minimize transmission losses
  • Automotive 12-volt lead-acid storage batterySupplies direct current (DC) via chemical reactions, driving electrons in a single continuous direction through the circuit
  • Standard residential North American wall receptacleDelivers alternating current (AC) that periodically reverses polarity and direction at a fixed frequency of 60 Hz60\text{ Hz}
  • Industrial metal electroplating tankRequires unidirectional direct current (DC) to continuously attract positively charged metal ions toward a single cathode

Answer

The correct matches pair the high-voltage transmission grid with AC transformer voltage stepping, the automotive lead-acid battery with unidirectional DC from chemical reactions, the residential wall receptacle with AC reversing at 60 Hz60\text{ Hz}, and the electroplating tank with unidirectional DC for steady metal ion deposition.
Direct current (DC) flows in one unchanging direction with steady polarity, which is produced by chemical batteries and required for electroplating. Alternating current (AC) periodically alternates its direction of flow, enabling transformers to step voltage levels efficiently for transmission and supplying standard 60 Hz60\text{ Hz} household power.

Step-by-Step Solution

1
Identify AC-dependent applications and their physical mechanisms
Recognize that power distribution grids and residential outlets utilize alternating current (AC). Grids depend on AC for transformer stepping, while outlets deliver cyclical 60 Hz60\text{ Hz} polarity reversals.
Transformers require time-varying current to induce secondary voltage, and utility generators produce sinusoidal alternating current.
2
Identify DC-dependent applications and their physical mechanisms
Recognize that lead-acid batteries and electroplating tanks operate on direct current (DC). Batteries generate unidirectional current chemically, while electroplating requires steady polarity to maintain ion migration.
Chemical cells produce static polarities, and reversing current in electroplating would dissolve rather than plate metal.
3
Match each application to its unique operational principle
Pair grid transmission to transformer stepping, battery to chemical unidirectional DC, wall outlet to 60 Hz60\text{ Hz} AC reversal, and electroplating to continuous ionic migration.
Each assignment links the fundamental behavior of alternating or direct current to its specific operational requirement.

Key Concept

Direct current (DC) maintains constant polarity and unidirectional electron flow, making it ideal for electrochemical storage (batteries) and electrodeposition. Alternating current (AC) reverses polarity periodically, enabling electromagnetic induction in transformers for long-distance power distribution and standard domestic utility delivery.
Estimated Time:1m 0s
Rate this question

Topics

Direct Current (DC) vs. Alternating Current (AC)

More questions from this topic