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Flashcards

Electromagnetic Waves

Uttar Pradesh Board · Class 12 · Physics

Flashcards for Electromagnetic Waves — Uttar Pradesh Board Class 12 Physics. Quick Q&A cards covering key concepts, definitions, and formulas.

43 questions22 flashcards5 concepts
22 Flashcards
Card 1Displacement Current

What is displacement current and who introduced this concept?

Answer

Displacement current is a current due to changing electric field, introduced by Maxwell. It is given by id = ε₀(dΦE/dt) where ΦE is electric flux. Maxwell introduced this concept to resolve inconsiste

Card 2Displacement Current

State the formula for displacement current and explain each term.

Answer

id = ε₀(dΦE/dt) where: - id = displacement current - ε₀ = permittivity of free space (8.85 × 10⁻¹² F/m) - ΦE = electric flux - dΦE/dt = rate of change of electric flux with time

Card 3Displacement Current

What inconsistency did Maxwell find in Ampere's circuital law for a charging capacitor?

Answer

When applying Ampere's law ∮B·dl = μ₀i to different surfaces with the same boundary around a charging capacitor, Maxwell found different values of current. For surfaces passing through the wire, curre

Card 4Maxwell's Equations

Write the Ampere-Maxwell law (generalized Ampere's law).

Answer

∮B·dl = μ₀ic + μ₀ε₀(dΦE/dt) where: - ic = conduction current - μ₀ε₀(dΦE/dt) = displacement current term This law states that magnetic field is produced by both conduction current and changing electric

Card 5Maxwell's Equations

List all four Maxwell's equations in vacuum.

Answer

1. ∮E·dA = Q/ε₀ (Gauss's law for electricity) 2. ∮B·dA = 0 (Gauss's law for magnetism) 3. ∮E·dl = -dΦB/dt (Faraday's law) 4. ∮B·dl = μ₀ic + μ₀ε₀(dΦE/dt) (Ampere-Maxwell law)

Card 6EM Wave Sources

What are the sources of electromagnetic waves?

Answer

Accelerated charges are the sources of electromagnetic waves. Neither stationary charges nor charges in uniform motion can produce electromagnetic waves. Examples include: - Oscillating charges - Acce

Card 7Nature of EM Waves

Describe the nature of electromagnetic waves in terms of field orientations.

Answer

In electromagnetic waves: 1. Electric field E and magnetic field B are perpendicular to each other 2. Both E and B are perpendicular to direction of wave propagation 3. E and B oscillate in phase (rea

Card 8EM Wave Equations

Write the mathematical representation of electromagnetic wave propagating along z-direction.

Answer

Ex = E₀ sin(kz - ωt) By = B₀ sin(kz - ωt) where: - E₀, B₀ = amplitudes - k = 2π/λ (wave number) - ω = 2πν (angular frequency) - kz - ωt = phase

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Electromagnetic Waves covers several key topics that are frequently asked in Uttar Pradesh Board Class 12 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.

Start by understanding all key concepts. Practise previous year questions from this chapter. Revise formulas and definitions regularly. Use flashcards for quick revision before the exam.

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