NDA cheat sheet for Electricity and Magnetism! 📱 Practice 1 Lakh+ PYQs on ExamBhai.com! - Free Study Material

Chapter Summary: Electricity and Magnetism

Mastering Electricity and Magnetism is essential for scoring high in the Physics section of the NDA examination. This study chapter consolidates fundamental principles, circuit rules, and electromagnetic field equations into a concise review structure.

1. Electrostatics

Electrostatics deals with charges at rest. Force between two point charges \(q_1\) and \(q_2\) separated by distance \(r\) is governed by Coulomb's Law:

\[F = \frac{1}{4\pi\varepsilon_0} \frac{q_1 q_2}{r^2}\]

Electric field intensity \(E\) at a point due to a charge \(q\) is given by \(E = \frac{F}{q} = \frac{1}{4\pi\varepsilon_0}\frac{q}{r^2}\). Electric potential \(V\) represents work done per unit charge: \(V = \frac{W}{q}\).

2. Current Electricity & Ohm's Law

Electric current \(I\) is the rate of flow of charge: \(I = \frac{Q}{t}\). Ohm's Law states that current is proportional to potential difference under constant conditions:

\[V = IR\]

Resistance depends on material properties and geometry: \(R = \varrho \frac{l}{A}\), where \(\varrho\) is resistivity. Power dissipated in a resistor is expressed as \(P = VI = I^2 R = \frac{V^2}{R}\).

3. Magnetism & Electromagnetism

Magnetic field \(B\) around a straight current-carrying wire at distance \(r\) is given by Biot-Savart Law application: \(B = \frac{\mu_0 I}{2\pi r}\). Force on a moving charge in a magnetic field is calculated via Lorentz Force:

\[F = qvB\sin\theta\]

Faraday's Law of Electromagnetic Induction states that induced electromotive force \(\mathcal{E}\) equals the rate of change of magnetic flux: \(\mathcal{E} = -\frac{d\Phi_B}{dt}\).