Electromagnetic waves — Flashcards
Tamil Nadu Board · Class 12 · Physics
25 flashcards for Electromagnetic waves (Tamil Nadu Board Class 12 Physics) to test yourself on key terms and facts.
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What is displacement current? Define it with the mathematical expression.
Answer
Displacement current is the current that comes into play in regions where the electric field (or electric flux) changes with time. It is defined as: i_d = ε₀(dΦ_E/dt) Where: - i_d = displacement cur…
Why did Maxwell introduce the concept of displacement current? What problem did it solve?
Answer
Maxwell introduced displacement current to resolve an inconsistency in Ampere's circuital law: 1. PROBLEM: When a capacitor is being charged, Ampere's law gave different results depending on the surf…
A parallel plate capacitor with plate area 50 cm² and separation 2 mm is connected to 220V AC supply at 50 Hz. Calculate the displacement current at t = 0.
Answer
Given: - A = 50 cm² = 50 × 10⁻⁴ m² = 0.005 m² - d = 2 mm = 2 × 10⁻³ m - V = 220√2 sin(2πft) = 311 sin(100πt) V - f = 50 Hz, so ω = 2πf = 100π rad/s - ε₀ = 8.85 × 10⁻¹² F/m Formula: i_d = ε₀(A/d)|dV/d…
State Maxwell's modified Ampere's law (Ampere-Maxwell law) in integral form.
Answer
Maxwell's Modified Ampere's Law (Ampere-Maxwell Law) in integral form: ∮_l B·dl = μ₀(i_c + i_d) = μ₀i_c + μ₀ε₀(dΦ_E/dt) Where: - ∮_l B·dl = line integral of magnetic field around closed loop - μ₀ = …
What are Maxwell's Four Equations in integral form? List all four with their meanings.
Answer
MAXWELL'S FOUR EQUATIONS (Integral Form): 1. GAUSS'S LAW (Electricity): ∮_S E·dA = Q_enclosed/ε₀ → Electric field lines begin on positive charges and end on negative charges 2. GAUSS'S LAW (Ma…
What is an electromagnetic wave? Describe its nature and key characteristics.
Answer
DEFINITION: An electromagnetic wave is a self-sustaining, non-mechanical wave produced by oscillating (accelerating) charges, consisting of coupled oscillating electric and magnetic fields. KEY CHARA…
How are electromagnetic waves produced? Explain using the concept of accelerating charges.
Answer
PRODUCTION OF ELECTROMAGNETIC WAVES: FUNDAMENTAL PRINCIPLE: Any accelerated charge produces electromagnetic waves. MECHANISM: 1. OSCILLATING CHARGE: When a charge oscillates about its mean position…
Describe Hertz's experiment. How did it confirm Maxwell's prediction?
Answer
HERTZ'S EXPERIMENT (1888): SETUP: - High voltage induction coil connected to two metal spheres - Spark discharged between spheres (transmitter) - Ring-shaped receiver kept at distance OBSERVATIONS: …
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