NEET · Physics doubts
180 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.