NEET doubts
700 doubts found
What does “Circular and helical motion” actually mean in Moving Charges & Magnetism, and why does it matter for NEET?
A velocity component perpendicular to B produces circular motion, while a parallel component remains unchanged. Together they make a helix whose pitch depends on the parallel speed.
What does “Hooke's law and elastic limit” actually mean in Mechanical Properties of Solids, and why does it matter for NEET?
For small deformation within the proportional limit, stress is proportional to strain. Beyond that range the graph need not remain linear, and beyond the elastic limit the body may not recover fully.
What does “Transverse nature” actually mean in Electromagnetic Waves, and why does it matter for NEET?
In a plane electromagnetic wave, electric field E and magnetic field B are perpendicular to each other and to the direction of propagation. Their cross-product direction E x B points along energy flow.
I keep getting “Significant figures” questions wrong in Units, Dimensions & Measurement. What's the trap?
keeping more digits in the answer than the least-precise measurement allows.
I keep getting “Acceleration” questions wrong in Kinematics. What's the trap?
assuming acceleration is zero whenever velocity is zero (e.g. at the top of a throw, v=0 but a=−g).
I keep getting “Newton's second law” questions wrong in Laws of Motion. What's the trap?
using a single force instead of the net (vector sum) force.
I keep getting “Work–energy theorem” questions wrong in Work, Energy & Power. What's the trap?
using only one force's work instead of the net work.
I keep getting “Torque” questions wrong in Rotational Motion. What's the trap?
using the force alone instead of force times perpendicular (lever-arm) distance.
I keep getting “Acceleration due to gravity g” questions wrong in Gravitation. What's the trap?
treating g as a fixed 9.8 everywhere, including in orbit.
I keep getting “Internal energy” questions wrong in Thermodynamics & Kinetic Theory. What's the trap?
thinking internal energy depends on pressure or volume for an ideal gas.
I keep getting “Time period of a pendulum” questions wrong in Oscillations & Waves. What's the trap?
thinking a heavier bob swings with a different period.
I keep getting “Electric field” questions wrong in Electrostatics. What's the trap?
treating field (a vector) and potential (a scalar) as the same thing.
I keep getting “Resistance and resistivity” questions wrong in Current Electricity. What's the trap?
confusing resistance (depends on shape) with resistivity (depends only on material and temperature).
I keep getting “Faraday's law of induction” questions wrong in Magnetism & Electromagnetic Induction. What's the trap?
expecting a steady (unchanging) magnetic field to induce an EMF.
I keep getting “Photon energy” questions wrong in Modern Physics. What's the trap?
treating light purely as a wave when explaining the photoelectric effect.
How does a small hydraulic jack let one person lift a whole car?
By Pascal's law, pressure applied to an enclosed fluid is transmitted equally everywhere.
A swimming pool always looks shallower than it really is — why, and by how much?
Light from the bottom bends away from the normal as it leaves the water, so your eye sees the bottom raised.
Why does light passing through a single very narrow slit spread into a broad bright band instead of a sharp line?
That's single-slit diffraction: every point of the slit acts as a wavelet source, and these wavelets interfere.
Why won't a transformer work on a DC supply?
A transformer works by mutual induction: the changing current in the primary makes a changing magnetic flux that induces a voltage in the secondary.
What actually happens inside a p–n junction the moment you forward-bias it?
At rest, a depletion region with a built-in barrier stops most carriers crossing.
What does “Independent horizontal and vertical motion” actually mean in Motion in a Plane, and why does it matter for NEET?
Gravity changes only the vertical velocity of a projectile. Horizontally, velocity stays constant when air resistance is ignored. The two motions share the same clock but otherwise evolve independently.
What does “Thermal expansion” actually mean in Thermal Properties of Matter, and why does it matter for NEET?
Most materials expand when heated because the average separation between particles increases. For an isotropic solid, area and volume expansion coefficients are approximately 2alpha and 3alpha when alpha is small.
What does “Temperature and molecular kinetic energy” actually mean in Kinetic Theory of Gases, and why does it matter for NEET?
For an ideal gas, absolute temperature measures average translational kinetic energy per molecule: 3k_BT/2. At the same temperature, light and heavy molecules have the same average translational energy but different rms speeds.
What does “Field-potential relationship” actually mean in Electrostatic Potential & Capacitance, and why does it matter for NEET?
The electric field points in the direction in which potential decreases most rapidly. Along one dimension E_x = -dV/dx; the minus sign carries the direction information.