Page 30 - Electrostatics-11

© GC Shiba
It is the nearest power of ‘ten’ used to approximate the measurement of a physical

quantity. It simply gives the rough estimate of the measurement.
For e.g., distance = 234567 km
5
= 2.23 × 10 km
5
= 2 × 10 km
5
~10 km
5
, = 10

Scalars and Vectors:

Scalar: The physical quantity having only magnitude but not direction is called
scalars. For e.g., distance, speed, mass, density, temperature, work, energy, power
etc.

Vectors: The physical quantity having both magnitude, direction and obey the

law of vector addition is called vectors. For e.g., displacement, velocity, force,
weight, torque, acceleration, electric field intensity, gravitational field intensity etc.

From the definition of vector, it is clear that only magnitude and direction
are not sufficient to consider physical quantity as vector. Current electricity has
both magnitude and direction still it is considered as a scalar.

Graphical representation of a vector

Tail or origin O P Head or tip

Vectors are represented by using straight line with an arrow. The length of straight
line represents the magnitude whereas the arrow represents the direction.

Generally, vectors are represented by using ordinary alphabet by providing arrow
⃗⃗
⃗ ⃗⃗
on their head. For e.g., , , , .
⃗
Types of vector:

̂
1) Unit vectors ( ): The vector having the magnitude of unity is called unit
vectors. Unit vectors are denoted by using ordinary alphabet with hat or cap

̂
on their head. Mathematically, = ⃗

| | ⃗⃗⃗
2) Equal vectors: Vectors having same magnitude and
⃗⃗
⃗
direction are called equal vectors. Here, ⃗⃗⃗

are equal vector.

7 Mechanics