NEET doubts
700 doubts found
I keep getting “Simple harmonic motion” questions wrong in Oscillations & Waves. What's the trap?
assuming every back-and-forth motion is SHM.
I keep getting “Coulomb's law” questions wrong in Electrostatics. What's the trap?
ignoring that like charges repel and unlike attract when assigning direction.
I keep getting “Ohm's law” questions wrong in Current Electricity. What's the trap?
assuming every component is ohmic (a diode or bulb filament is not).
I keep getting “Magnetic force on a moving charge” questions wrong in Magnetism & Electromagnetic Induction. What's the trap?
thinking the magnetic force can speed a charge up.
I keep getting “Photoelectric effect” questions wrong in Modern Physics. What's the trap?
thinking very bright low-frequency light can eject electrons.
Why does the roof of a house sometimes get lifted off during a storm even though the wind blows sideways, not up?
Fast-moving air over the roof lowers the pressure there (Bernoulli's principle: faster flow → lower pressure).
Why do stars twinkle at night but planets shine steadily?
A star is so far away it's effectively a point source; its thin beam gets randomly bent by moving pockets of air of different densities, so its brightness and position flicker — twinkling.
In Young's double-slit experiment, what happens to the fringes if I move the slits closer together?
Fringe width is β = λD/d, so it's inversely proportional to the slit separation d.
Why does a capacitor block DC but let AC pass?
A capacitor's opposition is Xc = 1/(ωC).
Why is a Zener diode used to keep a voltage steady (as a regulator)?
A Zener diode is designed to operate in reverse breakdown, where its voltage stays almost constant over a wide range of current.
What does “Resolving a vector into components” actually mean in Motion in a Plane, and why does it matter for NEET?
A vector is one arrow, but we may replace it by perpendicular x- and y-parts that together produce exactly the same effect. If the vector A makes angle theta with +x, then A_x = A cos(theta) and A_y = A sin(theta); signs come from the actual directions, not from the formula.
What does “Heat versus temperature” actually mean in Thermal Properties of Matter, and why does it matter for NEET?
Temperature tells how hot a body is and sets the direction of heat flow; heat is energy transferred because of a temperature difference. A bucket of warm water can contain more thermal energy than a cup of hotter water.
What does “Microscopic origin of gas pressure” actually mean in Kinetic Theory of Gases, and why does it matter for NEET?
Gas pressure comes from molecular collisions with container walls. Each collision changes molecular momentum; the wall experiences the equal and opposite momentum transfer spread over time and area.
What does “Potential as energy per charge” actually mean in Electrostatic Potential & Capacitance, and why does it matter for NEET?
Electric potential at a point is potential energy per unit test charge. Because it is a scalar, contributions from many source charges add algebraically with their signs.
What does “Magnetic dipole moment” actually mean in Magnetism & Matter, and why does it matter for NEET?
A bar magnet behaves like a magnetic dipole. Its moment points from south to north inside the magnet and determines the torque m x B in an external field.
What does “Rutherford scattering and nuclear atom” actually mean in Atoms, and why does it matter for NEET?
Most alpha particles pass through foil because atoms are mostly empty space; rare large deflections show that positive charge and most mass occupy a tiny nucleus.
What does “Nuclear size and density” actually mean in Nuclei, and why does it matter for NEET?
Nuclear radius scales as R = R_0 A^(1/3), so volume scales with nucleon number A. Because mass also scales with A, nuclear density is approximately constant across nuclei.
What does “Least count and instrument reading” actually mean in Experimental Skills, and why does it matter for NEET?
An instrument cannot honestly resolve changes smaller than its least count. A final reading combines the main-scale reading, coinciding-division contribution, and the zero-error correction with correct sign.
I keep getting “Wave speed, frequency and wavelength” questions wrong in Waves & Sound. What's the trap?
saying frequency changes when a wave enters another medium.
I keep getting “Magnetic force on a moving charge” questions wrong in Moving Charges & Magnetism. What's the trap?
using qvB when velocity is parallel to the field.
I keep getting “Stress and strain” questions wrong in Mechanical Properties of Solids. What's the trap?
giving strain the unit metre.
I keep getting “Changing fields sustain an electromagnetic wave” questions wrong in Electromagnetic Waves. What's the trap?
saying electromagnetic waves require a material medium.
What does “Significant figures” actually mean in Units, Dimensions & Measurement, and why does it matter for NEET?
the digits in a measurement that actually carry meaning, reflecting the instrument's precision.
What does “Acceleration” actually mean in Kinematics, and why does it matter for NEET?
the rate of change of velocity; it is a vector, so direction matters.