For an AC circuit, a phase diagram shows emf on X-axis, and current I is at angle θ to emf. Angle is phase angle θ between emf and current. Current I is resolved into two components, I cos θ is along emf on X-axis. I sine is along perpendicular direction to emf.
(A) Component I cos θ will draw the power from the source
(B) Component I sin θ will draw the power from the source
(C) I cos θ is called the powerless current
(D) I sin θ is called the powerless current
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) and (D) only
Given: In an AC circuit, current lags or leads emf by phase angle θ.
Current components:
• $I \cos \theta$ → component of current in phase with emf (active component)
• $I \sin \theta$ → component of current perpendicular to emf (reactive component)
Power is given by:
$P = E I \cos \theta$
Hence,
(A) Component $I \cos \theta$ will draw the power from the source — ✔ True
(B) Component $I \sin \theta$ will draw the power from the source — ✖ False
(C) $I \cos \theta$ is called the powerless current — ✖ False (it is the power component)
(D) $I \sin \theta$ is called the powerless current — ✔ True
Final Answer:
(A) and (D)