NEET doubts
700 doubts found
I keep getting “Bohr model” questions wrong in Modern Physics. What's the trap?
using a positive energy for a bound electron — bound states are negative.
Why does water climb up a thin glass tube on its own, while mercury actually goes down?
It's capillarity, set by whether the liquid wets the glass.
Why can a magnifying glass make text look bigger, and where must I hold it?
A magnifying glass is a convex lens.
Why can't the headlights of two different cars ever produce an interference pattern?
Interference needs coherent sources — a constant phase relationship.
To dim a light on AC, why is a choke (coil) better than a resistor?
A resistor would limit the current but waste the extra energy as heat.
I keep getting “Forward & reverse bias” questions wrong in Semiconductor Electronics (Diodes). What's the trap?
thinking a diode conducts equally both ways.
What does “Projectile trajectory” actually mean in Motion in a Plane, and why does it matter for NEET?
Eliminating time from x = u cos(theta)t and y = u sin(theta)t - gt^2/2 gives a quadratic y(x), so the ideal projectile path is a parabola.
What does “Calorimetry and thermal equilibrium” actually mean in Thermal Properties of Matter, and why does it matter for NEET?
In an insulated mixture, energy lost by hotter bodies equals energy gained by colder bodies until they reach a common temperature. Use signed heat changes or a clear lost = gained equation, never both conventions at once.
What does “Root-mean-square speed” actually mean in Kinetic Theory of Gases, and why does it matter for NEET?
The rms speed is the square root of the mean of v^2, not the ordinary mean speed. It links the molecular picture to measurable pressure and temperature.
What does “Equipotential surfaces” actually mean in Electrostatic Potential & Capacitance, and why does it matter for NEET?
Moving a charge along an equipotential surface requires no work by or against the electrostatic field. Electric-field lines cross equipotentials at right angles.
What does “Earth as a magnetic field” actually mean in Magnetism & Matter, and why does it matter for NEET?
Locally, Earth's field is described by declination, dip (inclination), and horizontal component. Dip is measured from the horizontal plane, not from the vertical.
What does “Hydrogen energy levels” actually mean in Atoms, and why does it matter for NEET?
Hydrogen bound-state energies are negative because zero is assigned to a free electron at infinity. Larger n means less negative energy and weaker binding.
What does “The mole” actually mean in Some Basic Concepts (Mole Concept), and why does it matter for NEET?
a counting unit for particles — one mole is 6.022×10²³ (Avogadro's number) of anything.
What does “Quantum numbers” actually mean in Structure of Atom, and why does it matter for NEET?
four numbers (n, l, m, s) that pin down an electron's shell, subshell, orbital orientation and spin.
What does “Octet rule” actually mean in Chemical Bonding & Molecular Structure, and why does it matter for NEET?
atoms tend to gain, lose or share electrons to reach eight in their outer shell.
What does “Enthalpy (H)” actually mean in Chemical Thermodynamics, and why does it matter for NEET?
the heat content at constant pressure; ΔH is negative for exothermic and positive for endothermic reactions.
What does “Dynamic equilibrium” actually mean in Equilibrium, and why does it matter for NEET?
the state where forward and reverse reactions occur at equal rates, so concentrations stay constant.
What does “Oxidation and reduction” actually mean in Redox Reactions, and why does it matter for NEET?
oxidation is loss of electrons and reduction is gain of electrons (remember OIL RIG).
What does “Atomic radius trend” actually mean in Periodic Table & Periodicity, and why does it matter for NEET?
atomic size decreases across a period (more nuclear pull) and increases down a group (new shells).
What does “Order of reaction” actually mean in Chemical Kinetics, and why does it matter for NEET?
the power to which a reactant's concentration is raised in the experimentally-determined rate law.
What does “Types of cells” actually mean in Electrochemistry, and why does it matter for NEET?
a galvanic cell turns a spontaneous reaction into electricity; an electrolytic cell uses electricity to drive a non-spontaneous reaction.
What does “Inductive effect” actually mean in Organic Chemistry — Basic Concepts, and why does it matter for NEET?
a permanent shift of electron density through sigma bonds due to electronegativity differences.
What does “Saturation” actually mean in Hydrocarbons, and why does it matter for NEET?
alkanes are saturated (only single bonds); alkenes and alkynes are unsaturated (double or triple bonds).
Why do people spread salt on icy roads and footpaths in winter?
Salt lowers the freezing point of water — a colligative effect.