Electric Field: Correct Definition
The electric field ($E$) at a point in space is defined as the force ($F$) experienced by a positive test charge ($q$) placed at that point, divided by the magnitude of the test charge.
The mathematical representation is:
$ E = \frac{F}{q} $
Where:
- E is the Electric Field Strength (measured in N/C or V/m)
- F is the Electric Force (measured in Newtons, N)
- q is the Test Charge (measured in Coulombs, C)
Analysis of Options
Let's analyze why Option 3 is the correct definition of the electric field:
- Option 1: Energy per unit area - This does not define the electric field. Concepts like intensity or pressure relate to energy per unit area.
- Option 2: Energy available per unit charge - This defines electric potential ($V$), not the electric field ($E$). Potential is related to the work done per unit charge.
- Option 3: Force acting per unit charge - This directly matches the definition of the electric field ($E = F/q$). It quantizes the force experienced in the field relative to the charge creating or interacting with it.
- Option 4: Force acting per unit mass - This defines the gravitational field strength ($g = F/m$), not the electric field.
Therefore, the correct definition highlights the force acting per unit charge.
Important Questions from Electric Fields and Gauss' Law
The surface charge density of a thin spherical shell placed in an air medium is 88.54 c/m2 The intensity of the electric field measured 12 mm outside the shell from the centre of the shell is 5.625 × 101 2 N/C. The thin spherical shell has a radius of:
The expression for torque '\(\vec{\tau}\)' experienced by an electric dipole of dipole moment '\(\vec{P}\)' in an external uniform electric field '\(\vec{E}\)' is given by :
The electric flux passing through a surface of area A = 8j m2 in an electric field vector E = 2i + 3j - 4k V/m (bold is for vectors) is:
- Let a total charge $2Q$ be distributed in a sphere of radius $R$, with the charge density given by $\rho(r) = Cr^2$, where $r$ is the distance from the centre. Two charges $A$ and $B$, of $-Q$ each, are placed on diametrically opposite points, at equal distance, '$a$' from the centre. If $A$ and $B$ do not experience any force, then:
- Two point charges $q_1 \left( {\sqrt {10} {\rm{\mu C}}} \right)$ and $q_2(-18\sqrt{2} {\rm{\mu C}})$ are placed on the x-axis at $x = 0$ m and $x = 4$ m respectively. The electric field (in V/m) at a point $(1, 3)$ m is,
$\left[ {{\rm{Take\;}}\frac{1}{{4{\rm{\pi }}{\epsilon_0}}} = 9 \times {{10}^9}{\rm{N}}{{\rm{m}}^2}{{\rm{C}}^{ - 2}}} \right]$
