Reading the Argand plane: The point labelled +4 on the complex plane represents which position relative to the origin?

Difficulty: Easy

Correct Answer: 4 units right of the origin on the real axis

Explanation:


Introduction / Context:
The Argand (complex) plane is a visual tool for representing complex numbers where the horizontal axis is the real part and the vertical axis is the imaginary part (often denoted by j in electrical engineering). Understanding this mapping is useful for visualizing phasors, impedances, and frequency responses.


Given Data / Assumptions:

  • The label +4 without a j indicates a purely real number: 4 + j0.
  • Standard axes: real axis horizontal, imaginary axis vertical.


Concept / Approach:
A purely real number positions entirely along the real axis. A positive real value lies to the right of the origin, while a negative real value lies to the left. Imaginary values would place the point along the vertical axis instead.


Step-by-Step Solution:

Interpret +4 as the complex number 4 + j0.Map to the plane: move 4 units along the positive real (horizontal) axis from the origin; no movement along the j axis.Therefore, the point is 4 units right of the origin on the real axis.


Verification / Alternative check:
Polar representation: magnitude = 4, angle = 0°. An angle of 0° aligns with the positive real axis, confirming location to the right of the origin.


Why Other Options Are Wrong:

  • Left on the real axis: would correspond to −4.
  • Above or below on the j axis: would require a nonzero imaginary part (±j4).


Common Pitfalls:

  • Confusing the j axis as horizontal; by convention it is vertical in engineering contexts.


Final Answer:
4 units right of the origin on the real axis

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