Question

Which of the following is scalar
A. Current
B. Velocity
C. Force
D. Acceleration

Answer 1

Basically physical quantities can be divided into vectors and scalars. Scalars have magnitude that means the value. But the vector has both magnitude and direction. For any vector we can denote in the form of magnitude and the direction where that vector is pointing.

Complete answer:
In order to represent a vector first we should have one coordinate system. There will be one reference point called origin. There will be 2 reference axes if we consider only a two dimensional plane and there will be three reference axes if we consider three dimensional space.
All these axes will be mutually perpendicular. The point of intersection of these axes will be the origin.
Let $\mathop r\limits^ \to$ be the vector and this vector will have both magnitude and direction. Magnitude of vector will be $\left| r \right|$ while the direction of this vector will be along $\mathop r\limits^ \wedge$. $\mathop r\limits^ \wedge$ is called as unit vector
From the formula $\mathop r\limits^ \to = \left| r \right|\mathop r\limits^ \wedge$ we get unit vector as $\dfrac{{\mathop r\limits^ \to }}{{\left| r \right|}} = \mathop r\limits^ \wedge$.
From the above given options velocity has magnitude and direction and follows vector addition. So it is a vector. Force has magnitude and direction and follows vector addition. So it is a vector. Acceleration has magnitude and direction and follows vector addition. So it is a vector.
Current also has magnitude and direction. But it is not a vector because it doesn’t follow vector law of addition. So it is a scalar.

Hence option A is the answer.

Note:
From this one thing is clear that every physical quantity which has magnitude and direction is not a vector. It should follow vector laws. In the same way pressure is also not a vector. Interesting fact is even though velocity is a vector, velocity of light is not a vector.