JEE doubts
500 doubts found
What is the difference between systematic error and random error?
Systematic errors are consistent and one-directional (fixable by calibration); random errors scatter both ways (reduced by averaging).
What is the difference between distance and displacement?
Distance is the total path length (scalar, never decreases); displacement is the straight-line vector from start to finish (can be zero on a round trip).
What is the difference between static friction and kinetic friction?
Static friction acts on a stationary object and self-adjusts up to a limit; kinetic friction acts on a sliding object and is roughly constant (and usually smaller).
What is the difference between elastic collision and inelastic collision?
Both conserve momentum; an elastic collision also conserves kinetic energy, while an inelastic one converts some KE into heat/deformation.
What is the difference between torque and force?
Force causes linear acceleration; torque causes angular acceleration and depends on where the force is applied.
What is the difference between orbital velocity and escape velocity?
Orbital velocity keeps a satellite in a circular orbit; escape velocity (√2 times larger) lets it leave gravity forever.
What is the difference between C_p and C_v?
C_p (constant pressure) exceeds C_v (constant volume) because at constant pressure some heat also does expansion work.
What is the difference between mechanical wave and electromagnetic wave?
Mechanical waves need a medium (sound); electromagnetic waves (light) travel through vacuum.
What is the difference between conductor and insulator?
A conductor has free charges that move easily; an insulator holds its charges in place.
What is the difference between resistance and resistivity?
Resistance (Ω) depends on the object's size and shape; resistivity (Ω·m) is an intrinsic material property.
What is the difference between AC and DC?
Alternating current periodically reverses direction (mains supply); direct current flows one way (batteries).
What is the difference between nuclear fission and nuclear fusion?
Fission splits a heavy nucleus into lighter ones (reactors); fusion joins light nuclei into a heavier one (the Sun) — both release energy.
When do I use Δ(AB)/AB = ΔA/A + ΔB/B in Units, Dimensions & Measurement, and what does it mean?
the fractional error of a product equals the sum of fractional errors.
What is the difference between speed and velocity?
Speed is a scalar (how fast); velocity is a vector (how fast AND in which direction).
What is the difference between mass and weight?
Mass is the amount of matter (kg, same everywhere); weight is the gravitational force on it (N, changes with g).
When do I use W = Fd cosθ in Work, Energy & Power, and what does it mean?
work done by a constant force.
What is the difference between moment of inertia and mass?
Mass resists linear acceleration; moment of inertia resists angular acceleration and also depends on the shape and axis.
What is the difference between g at height and g at depth?
Above the surface g ∝ 1/(R+h)²; below the surface g decreases roughly linearly to zero at the centre.
When do I use ΔU = Q − W in Thermodynamics & Kinetic Theory, and what does it mean?
first law: change in internal energy from heat and work.
When do I use T = 2π√(m/k) in Oscillations & Waves, and what does it mean?
period of a mass on a spring.
When do I use F = kq₁q₂/r² in Electrostatics, and what does it mean?
Coulomb force between point charges.
When do I use V = IR in Current Electricity, and what does it mean?
Ohm's law relating voltage, current and resistance.
When do I use F = qvB sinθ in Magnetism & Electromagnetic Induction, and what does it mean?
force on a charge moving through a magnetic field.
What is the difference between n-type semiconductor and p-type semiconductor?
n-type is doped to have extra free electrons (negative carriers); p-type is doped to have holes (positive carriers).