Select scalar quantities from the following:
A. electric flux
B. Electric current
C. Current density
D. Electromotive force (EMF)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, B and D only
A scalar has magnitude only and adds algebraically; a vector also has a direction and adds by the parallelogram rule.
(A) electric flux — Scalar. It is the dot product \( \Phi = \vec{E}\cdot\vec{A} \) of two vectors, which is a scalar.
(B) Electric current — Scalar. Current has a sense along the wire, but currents at a junction add algebraically, not by the parallelogram law.
(C) Current density — Vector. \( \vec{J} \) is the current per unit area in the direction of the flow of positive charge, \( \vec{J} = \sigma\vec{E} \).
(D) Electromotive force (EMF) — Scalar. The emf of a source is the work done per unit charge, \( \varepsilon = W/q \), and has no direction.