Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Alternating Current () is an electric current that reverses its direction periodically with time.
Direct Current () always flows in one direction and does not change its polarity.
In India, the frequency of supply is . This means the current changes its direction every .
One major advantage of over is that electric power can be transmitted over long distances without much loss of energy using step-up transformers.
Most residential power outlets provide , while batteries and solar cells provide .
The time period () is the time taken to complete one full cycle of the wave, and frequency () is the number of cycles per second.
📐Formulae
💡Examples
Problem 1:
If the frequency of alternating current in a circuit is , calculate the time interval after which the current reverses its direction.
Solution:
Given . The current reverses its direction twice in one complete cycle. Therefore, the time interval to reverse direction is . Substituting the value: .
Explanation:
In an cycle of , there are cycles per second. Since the current goes from zero to maximum, back to zero, then to maximum in the opposite direction and back to zero in one cycle, it changes direction every half-cycle.
Problem 2:
Identify the type of current represented by a graph where the magnitude of current remains constant and the direction does not change over time.
Solution:
The current is Direct Current ().
Explanation:
By definition, flows in a single direction and its magnitude remains constant (if it is steady ), whereas would show a sinusoidal wave pattern alternating between positive and negative values.