NEET PREP | APRIL 2026
NEET UG 2027 — CHAPTER-WISE MCQ PRACTICE | PHYSICS
• Subject: Physics (Class XII, Chapter 1)
• Expected questions: 3–5 per year from Electrostatics
• Difficulty: Moderate to High
• NCERT Class: XII — Chapters 1 & 2 (Electric Charges, Fields, and Potential)
Electrostatics is the most important topic in NEET Physics, contributing 3–5 questions every year. NCERT Class 12 Physics Chapters 1 and 2 cover the entire scope: Coulomb’s Law, electric fields and field lines, Gauss’s Law, electric potential and potential energy, capacitors, and dielectrics. Mastery of key formulas and conceptual understanding of field behaviour is essential to score full marks from this chapter.
Strengthen your physics preparation with our NEET coaching program. Practice chapter-wise on our free NEET mock test. Download the full NEET Physics syllabus.
1. Coulomb’s Law and Electric Field — Fundamentals
• Acts between point charges; along the line joining them
• Coulomb constant k = 9 × 10⁹ N·m²/C² (= 1/4πε₀)
• ε₀ = 8.854 × 10⁻¹² C²/N·m² (permittivity of free space)
• In a medium with dielectric constant K: F = kq₁q₂/Kr²
• Electric field lines: start from +q, end at −q; never intersect; density ∝ field strength
• Coulomb’s Law: F = kq₁q₂/r² (in vacuum)
• Electric Field: E = F/q₀ = kQ/r² (due to point charge Q)
• Electric Field on axis of dipole: E = 2kp/r³
• Electric Field on equatorial plane of dipole: E = kp/r³
• Dipole moment: p = q × 2l (SI unit: C·m)
2. Gauss’s Law, Electric Potential, and Capacitors
Gauss’s Law states that the total electric flux through any closed surface equals the enclosed charge divided by ε₀: Φ = Q_enclosed / ε₀. This law is particularly powerful for finding electric fields of symmetric charge distributions.
• Electric Potential: V = kQ/r (due to point charge Q)
• Potential difference: V_A − V_B = W_AB / q
• Relation: E = −dV/dr (E points from high V to low V)
• Equipotential surface: Work done = 0; field ⊥ to surface
• Capacitance: C = Q/V = ε₀A/d (parallel plate, air)
• With dielectric: C = Kε₀A/d
• Energy stored: U = ½CV² = Q²/2C = QV/2
• Capacitors in series: 1/C = 1/C₁ + 1/C₂
• Capacitors in parallel: C = C₁ + C₂
| Configuration | Electric Field E | Electric Potential V |
|---|---|---|
| Point charge Q at distance r | kQ/r² | kQ/r |
| Conducting sphere (outside, r>R) | kQ/r² | kQ/r |
| Conducting sphere (inside, r<R) | Zero | kQ/R (constant) |
| Infinite plane sheet (charge density σ) | σ/2ε₀ | Non-uniform |
| Between parallel plates (capacitor) | σ/ε₀ = V/d | V = Ed |
C = ε₀A/d (Capacitance = epsilon-zero × Area / distance)
Remember: Dielectric INCREASES C; increasing d DECREASES C; increasing A INCREASES C.
• Charge is quantized: q = ne (n = integer, e = 1.6 × 10⁻¹⁹ C)
• Charge is conserved — net charge of isolated system is constant
• Inside conductor: E = 0; all charge resides on outer surface
• Surface charge density is highest at sharp points (corona discharge)
• Van de Graaff generator uses this principle to accumulate charge
3. NEET 2027 — 10 MCQ Practice Questions
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4. Frequently Asked Questions (FAQ)
Q1: What is the difference between electric potential and electric potential energy?
Electric potential (V) is a property of the point in the field — it is the work done per unit positive test charge in bringing it from infinity to that point (V = W/q₀). Electric potential energy (U) is the energy of a specific charge q at that point: U = qV.
Q2: Why is electric field zero inside a conductor?
In electrostatic equilibrium, free electrons in the conductor redistribute until the net internal field is zero. Any excess charge resides entirely on the outer surface. This is why a Faraday cage shields interior from external electric fields.
Q3: What is polarization of a dielectric?
When a dielectric is placed in an electric field, the bound charges within its atoms/molecules shift slightly — positive charges move in the field direction and negative charges opposite. This creates induced dipoles, reducing the net internal field. The dielectric constant K measures this reduction.
Q4: How does inserting a dielectric between capacitor plates affect energy stored?
If the capacitor is isolated (constant Q): inserting dielectric increases C, so U = Q²/2C decreases. If connected to a battery (constant V): inserting dielectric increases C, so U = ½CV² increases.
Q5: What is the principle of superposition in electrostatics?
The force on any charge due to a number of other charges is the vector sum of forces due to each individual charge. Electric fields from multiple sources also add vectorially. This is the basis for solving complex charge distribution problems.
Last Updated: April 2026