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Electromagnetic Waves

Telangana Open School (TOSS) · Class 12 · Physics

Flashcards for Electromagnetic Waves — Telangana Open School (TOSS) Class 12 Physics. Quick Q&A cards covering key concepts, definitions, and formulas.

53 questions30 flashcards3 concepts

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30 Flashcards
Card 1Displacement Current

What is displacement current? Why is it necessary?

Answer

Displacement current is a current due to a changing electric field in space or capacitor gap, given by $ i_d = \varepsilon_0 \frac{d\phi_E}{dt} $. It is necessary to maintain continuity of current in

Card 2Maxwell's Equations

State the Ampere-Maxwell law.

Answer

The Ampere-Maxwell law is: $ \oint \vec{B} \cdot \vec{dl} = \mu_0 (i_c + i_d) = \mu_0 i_c + \mu_0 \varepsilon_0 \frac{d\phi_E}{dt} $. It states that magnetic fields are produced by both conduction cur

Card 3Displacement Current

A parallel plate capacitor is being charged by a current of 1.5 A. What is the displacement current between the plates?

Answer

Displacement current $ i_d $ equals the conduction current in the wire. Given: $ i_c = 1.5 \, \text{A} $. Therefore, $ i_d = 1.5 \, \text{A} $.

Card 4Maxwell's Theory

How does a changing electric field produce a magnetic field?

Answer

According to Maxwell, a time-varying electric field generates a magnetic field, just as a current does. This is the displacement current effect. For example, during capacitor charging, the changing el

Card 5EM Wave Properties

An EM wave has electric field amplitude $ E_0 = 120 \, \text{N/C} $. Find the magnetic field amplitude.

Answer

Use $ B_0 = \frac{E_0}{c} $. $ c = 3 \times 10^8 \, \text{m/s} $. Step 1: $ B_0 = \frac{120}{3 \times 10^8} = 4 \times 10^{-7} \, \text{T} $. Answer: $ 4 \times 10^{-7} \, \text{T} $.

Card 6EM Wave Properties

What is the speed of electromagnetic waves in vacuum?

Answer

The speed is $ c = \frac{1}{\sqrt{\mu_0 \varepsilon_0}} = 3 \times 10^8 \, \text{m/s} $. This is the speed of light, confirming that light is an EM wave.

Card 7EM Wave Properties

An EM wave propagates in the x-direction with $ E = 8.1 \, \text{V/m} $. Find $ B $ at that point.

Answer

Use $ B = \frac{E}{c} $. $ c = 3 \times 10^8 \, \text{m/s} $. Step 1: $ B = \frac{8.1}{3 \times 10^8} = 2.7 \times 10^{-8} \, \text{T} $. Answer: $ 2.7 \times 10^{-8} \, \text{T} $.

Card 8Nature of EM Waves

Write the expressions for electric and magnetic fields in an EM wave propagating along z-axis.

Answer

Electric field: $ E_x = E_0 \sin(kz - \omega t) $. Magnetic field: $ B_y = B_0 \sin(kz - \omega t) $. Both are perpendicular to each other and to the direction of propagation.

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What are the important topics in Electromagnetic Waves for Telangana Open School (TOSS) Class 12 Physics?
Electromagnetic Waves covers several key topics that are frequently asked in Telangana Open School (TOSS) Class 12 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Electromagnetic Waves — Telangana Open School (TOSS) Class 12 Physics?
Understand the core concepts first, then work through the 53 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
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