1. What is Electric Charge?

Fundamental property of matter by which it can attract or repel other matter.

Two types:

Positive charge
Negative charge

SI Unit: Coulomb (C)

GenZ Example

Like how your wool sweater sticks to your hair — electrostatic force.

2. Important AAI ATC Focused Concepts

3. Coulomb’s Law

The force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.

\( F = k \frac{q_1 q_2}{r^2} \)

Where:

F: Force between charges (N)
q₁, q₂: Charges (C)
r: Distance between them (m)
k: Coulomb constant (9 × 10⁹ Nm²/C²)

Nature:

Attractive for unlike charges
Repulsive for like charges

PYQ Type: Theory MCQ on law’s nature

4. Electric Field (E)

Definition: Force per unit positive charge at a point in an electric field.

\( E = \frac{F}{q} \) or \( E = k \frac{Q}{r^2} \)

Unit: N/C

GenZ Example

Near a charged comb → small paper bits get attracted due to electric field.

PYQ Type: Formula identification MCQ

5. Electric Field Lines

Properties:

Emerge from positive charge
End at negative charge
Never cross each other
Denser lines = stronger field

PYQ Type: Theory MCQ area

6. Electric Dipole

A pair of equal and opposite charges separated by a small distance.

Dipole Moment (p):

\( p = q \times 2a \)

Unit: C·m

Electric Field on Axial Line:

\( E_{axial} = \frac{1}{4\pi \epsilon_0} \frac{2p}{r^3} \)

Electric Field on Equatorial Line:

\( E_{equatorial} = \frac{1}{4\pi \epsilon_0} \frac{p}{r^3} \)

PYQ Type: Theory concept MCQ

7. Electric Flux (Φ)

The measure of electric field passing through a given area.

\( \Phi = E \cdot A \)

Where:

E: Electric field
A: Area perpendicular to field

Unit: Nm²/C

PYQ Type: Occasionally asked

8. AAI ATC PYQ Analysis (2021–2023)

2021 Shift 2: Coulomb’s law nature MCQ

2022 Shift 1: Unit of electric field (N/C)

2023 Feb Shift 1: Electric field lines properties MCQ

9. Electric Charges & Fields Formula Quick Revision Sheet

Formula	Meaning
\( F = k \frac{q_1 q_2}{r^2} \)	Coulomb’s law
\( E = \frac{F}{q} \)	Electric field
\( E = k \frac{Q}{r^2} \)	Electric field due to a point charge
\( p = q \times 2a \)	Dipole moment
\( \Phi = E \times A \)	Electric flux

10. Quick Concept Recap

Concept	GenZ Example
Like charges repel	Rubbing two balloons apart
Electric field attracts neutral objects	Charged comb picks paper
Field lines denser = stronger field	Near comb tip, stronger pull
Dipole = +q and –q pair	Like a small magnet with two poles

11. Final AAI ATC Takeaway

Focus Areas:

1–2 theory or formula-based MCQs per year
Coulomb’s law formula + nature
Unit of electric field
Electric field lines properties
Dipole concept and formula
Electric flux definition