Important Derivations for Class 12 Physics Chapter 8 Electromagnetic Waves

Important Derivations for Class 12 Physics Chapter 8 Electromagnetic Waves

(1) Derive expression for displacement current

The electric flux between the plates of a capacitor is given by $$ \begin{aligned} & \phi_{\mathrm{E}}=\mathrm{EA}=\frac{\mathrm{Q}}{\varepsilon_0 \mathrm{~A}} \cdot \mathrm{A}=\frac{\mathrm{Q}}{\varepsilon_0} \\ & \quad \frac{\mathrm{d} \phi_{\mathrm{E}}}{\mathrm{dt}}=\frac{\mathrm{d}}{\mathrm{dt}}\left(\frac{\mathrm{Q}}{\varepsilon_0}\right)=\frac{1}{\varepsilon_0} \frac{\mathrm{dQ}}{\mathrm{dt}} \\ & \quad \frac{\mathrm{d} \phi_{\mathrm{E}}}{\mathrm{dt}}=\frac{1}{\varepsilon_0} \mathrm{i} \quad \quad\left(\text { As, } \mathrm{i}=\frac{\mathrm{dQ}}{\mathrm{dt}}\right) \\ & \quad \mathrm{i}=\varepsilon_0\left(\frac{\mathrm{d} \phi_{\mathrm{E}}}{\mathrm{dt}}\right) \end{aligned} $$

(2) Velocity of propagation of an electromagnetic wave

c = E₀/B₀

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Why students face difficulty in physics derivations?

There can be several reasons why students face difficulty in physics derivations, including:

1. Lack of foundation: A lack of understanding of the underlying concepts and principles can make it difficult to follow the logical steps in a derivation.
2. Mathematical background: Physics often involves complex mathematical calculations, and students who struggle with math may find it challenging to perform the necessary calculations.
3. Limited practice: Regular practice is key to developing the skills required for physics derivations, and students who have limited practice opportunities may struggle.
4. Poor problem-solving skills: Physics problems often require creative problem-solving skills, and students who struggle with this aspect of physics may find derivations particularly challenging.
5. Limited exposure to different problems: Physics derivations can vary widely in their level of complexity, and students who have limited exposure to different types of problems may struggle when faced with a new challenge.
6. Confusion with notation: Physics often uses a specialized notation, and students who are unfamiliar with this notation may struggle to follow the steps in a derivation.

Remembering physics derivations can be a challenge, but here are some tips that may help:

1. Practice, practice, practice: Regularly practicing physics derivations helps to build muscle memory and improve recall.
2. Visualize the process: Try to visualize the steps involved in a derivation, as well as the physical meanings behind each equation.
3. Make connections: Try to relate each step of the derivation to a concept or formula you already know, which can help to reinforce your understanding.
4. Write it down: Writing out a derivation helps to solidify your understanding and makes it easier to remember.
5. Understand the physical meaning: Try to understand the physical meaning behind each equation, which can help you to remember the derivation in a broader context.
6. Teach someone else: Teaching someone else the derivation can be a great way to reinforce your understanding and remember it more easily.
7. Use mnemonics: Creating mnemonics or acronyms can be a helpful way to remember a series of steps in a derivation.

Remember, it takes time and consistent effort to remember physics derivations. Keep practicing and seeking help when needed, and you will likely see improvement over time.

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