CRACKNEETPhysics

⚡ 3000+ FREE Physics videos. 4000 FREE MCQs. One channel. Every major exam. Start learning smarter, not costlier.

electromagnetic Induction + Mutual Induction + Transformer Logic

Two coils, Coil P and Coil S, are placed close to each other but are electrically isolated. Coil P is connected to a sinusoidal AC source, while Coil S is connected to an external resistor R. The number of turns in Coil S is twice that of Coil P. Assume perfect magnetic coupling and negligible resistance of the coils.

Which of the following statements are correct?

(A) If the rate of change of current in Coil P becomes zero at any instant, the induced emf in Coil S is also zero at that instant.

(B) Doubling the number of turns of Coil S doubles the induced current in Coil S under all conditions.

(C) Increasing the resistance connected to Coil S decreases the induced emf in Coil S.

(D) The induced current in Coil S reverses direction every half cycle of the AC source.

(1) A and D only

(2) A, B and D only

(3) B and C only

(4) A, C and D only

11 hours ago | [YT] | 0

CRACKNEETPhysics

⚡ Concept > Formula > Logic > Answer

Imagine Coil 1 as the "creator" and Coil 2 as the "receiver." When AC flows through Coil 1, its current keeps changing with time (dI1//dt). A changing current creates a changing magnetic field, which produces a changing magnetic flux (dΦ/dt) through Coil 2. According to Faraday's Law, this changing flux induces an emf in Coil 2:

e₂ = -N₂ (dΦ/dt)

The negative sign comes from Lenz's Law, which tells us that the induced emf always opposes the change that produces it.

🎯 Remember these 4 exam-winning concepts:
✅ More turns in Coil 2 → Higher induced emf is possible.
✅ Current in Coil 2 depends on its impedance (Resistance + Inductance).
✅ Voltage is not always greater or smaller. It depends on the turns ratio.
✅ The frequency of the induced emf is exactly the same as the AC source connected to Coil 1.

🚀 NEET/JEE Tip: Don't memorize formulas blindly. First identify the cause: Changing Current → Changing Flux → Induced EMF → Induced Current. Once this chain is clear, transformer and electromagnetic induction questions become surprisingly easy.

Selection Walla Channel | Concepts First. Marks Follow. 🎓

11 hours ago | [YT] | 0

CRACKNEETPhysics

📚 Concepts > Cramming.

⚡ 3000+ FREE Physics videos. 4000 FREE MCQs. One channel. Every major exam. Start learning smarter, not costlier.

1 day ago | [YT] | 1

CRACKNEETPhysics

No Slip = Legit Roll! 😎 Bottom is Frozen ⚓ | Top is Turbo ⚡ (2v)


www.youtube.com/playlist?list...

2 days ago (edited) | [YT] | 3

CRACKNEETPhysics

3000+ Videos + 4000+ MCQs = Your Physics Power-Up. FREE. 🎮

🧠 NEET Physics Challenge

A rigid body is rotating about a fixed axis. The graph between angular position (θ) and time (t) is a straight line with a positive slope.

Which of the following statements is INCORRECT?

A. The angular velocity of the body is constant.

B. The angular acceleration of the body is zero.

C. The body must be rotating in the anticlockwise direction throughout the motion.

D. If the angular position θ is negative at some instant, the body must be rotating clockwise at that instant.

https://youtu.be/HRla6iTKhmM

2 days ago | [YT] | 0

CRACKNEETPhysics

🚀 NEET Aspirants, Read This!

Why chase expensive coaching when 3000+ Physics videos, 700+ recorded LIVE classes, and 4000+ concept-based MCQs are waiting for you... FREE! 🔥

No rote learning. No shortcuts. Just crystal-clear concepts that help you solve any question.

📍Selection Walla Channel
Concepts First. Rank Follows. 💯

3 days ago | [YT] | 7

CRACKNEETPhysics

🚀 NEET Aspirants, Read This!

Why chase expensive coaching when 3000+ Physics videos, 700+ recorded LIVE classes, and 4000+ concept-based MCQs are waiting for you... FREE! 🔥

No rote learning. No shortcuts. Just crystal-clear concepts that help you solve any question.

📍Selection Walla Channel
Concepts First. Rank Follows. 💯

3 days ago | [YT] | 3

CRACKNEETPhysics

📘 Standing Waves – Conceptual Exam Notes (NEET/JEE/Class 11)

A standing (stationary) wave is formed when two identical progressive waves of the same frequency, wavelength, and amplitude travel in opposite directions in the same medium and undergo continuous superposition. Unlike progressive waves, a standing wave does not transfer energy from one place to another because the energy oscillates locally between kinetic and potential forms.

The wave consists of nodes, where the displacement is always zero, and antinodes, where the displacement is maximum. The distance between two successive nodes or two successive antinodes is λ/2, while the distance between a node and the nearest antinode is λ/4. All particles between two adjacent nodes vibrate in the same phase, whereas particles in adjacent loops vibrate 180° out of phase. The positions of nodes and antinodes remain fixed, but the displacement of particles changes continuously with time.

At certain instants, such as t = T/4, the entire string passes through its mean position because the two constituent waves become completely out of phase, making the instantaneous displacement zero everywhere. This does not mean the standing wave disappears; it simply represents one stage in its oscillation cycle.

Understanding the formation, phase relationship, nodes, antinodes, and time evolution of standing waves is essential for solving conceptual and numerical questions in NEET, JEE, and Class 11 Physics.

Save your parents' hard-earned money. Invest your time instead. That's the strategy that compounds. 📚⚡

4 days ago | [YT] | 6

CRACKNEETPhysics

Before spending lakhs, spend 30 minutes here. Your Physics might thank you. 😉
One channel. 3000+ videos. 4000+ MCQs. Zero excuses. 🔥


🧠 NEET Physics Concept Challenge


❓Identify the INCORRECT statement about Mechanical Waves.



A. A transverse mechanical wave requires the medium to possess shear elasticity. Hence, it generally propagates through solids but not through fluids.

B. The speed of a wave in a stretched string increases if the tension is increased while the mass per unit length remains unchanged.

C. Every mathematical function of the form f(x − vt) represents a physically possible progressive wave.

D. During beats, the pitch heard by the listener is equal to the average of the two frequencies, while the loudness changes periodically.





✅ Correct Answer: C

Statement C:
"Every mathematical function of the form f(x − vt) represents a physically possible progressive wave."

❌ This statement is INCORRECT.

Many students remember only one condition:

✅ A progressive wave must be of the form f(x ± vt).

However, this is not sufficient.

A physically possible wave must satisfy two conditions:

It must be of the form f(x ± vt).
Its displacement must always remain finite (bounded).
🤔 What is a Bounded Function?

A bounded function is one whose value never becomes infinitely large.

In simple words,

The displacement of a particle in a wave cannot become infinite.

Every particle in a real medium can move only by a limited distance from its mean position.

✅ Example of a Bounded Wave

y = A sin(kx − ωt)

The sine function always lies between −1 and +1.

Therefore,

−A ≤ y ≤ +A

The displacement is always finite.

Hence, it represents a physically possible wave.

❌ Example of an Unbounded Function

y = e^(x − vt)

Although it is of the form f(x − vt),

its value keeps increasing without limit as x increases.

This would mean particles of the medium move by an infinitely large displacement, which is physically impossible.

Hence, it cannot represent a real wave.

🎯 NEET Learning Point

Every physical progressive wave is of the form f(x ± vt), but not every function of the form f(x ± vt) represents a physical wave.

A valid wave equation must satisfy both:

✅ Correct mathematical form f(x ± vt)

AND

✅ Bounded (finite) displacement throughout the medium.

This is a classic conceptual trap in NEET examinations.

4 days ago | [YT] | 1

CRACKNEETPhysics

📢 A Message from Rohit Sir

Dear Students,

Why spend thousands on expensive coaching when 3000+ recorded Physics lectures and 4000+ exam-oriented MCQs are available FREE on Selection Walla Channel?

Whether you're preparing for NEET, JEE Main, CBSE, WBJEE, CUET, BITSAT, KCET, MHET, IB BOARD, Cambridge or any competitive exam with Physics, this channel provides high-quality recorded live classes, conceptual learning, and extensive practice to strengthen your preparation.

Learn Concepts. Practice MCQs. Build Confidence. Save Your Parents' Hard-Earned Money.

Happy Learning! 🚀
– Rohit Sir
Selection Walla Channel

4 days ago | [YT] | 4