RBSE SS Physics flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Coulomb's law

The electrostatic force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation, acting along the joining line.

Electric flux

The number of field lines crossing a surface, computed as the surface integral of the electric field over that area; SI unit is N·m²/C.

Capacitance

The ratio of charge stored on a conductor to its potential, C = Q/V, measured in farads; one farad equals one coulomb per volt.

Drift velocity

The small average velocity acquired by free electrons along a conductor under an applied field, typically of order 10⁻⁴ m/s, related to current by I = nAev_d.

Kirchhoff's junction rule

At any node the sum of currents entering equals the sum leaving, expressing conservation of charge in a steady-current circuit.

Internal resistance

The resistance within a cell that causes its terminal voltage to fall below the EMF when current flows, so V = ε − Ir.

Biot–Savart law

The magnetic field due to a small current element is proportional to current, element length, and the sine of the angle, and inversely proportional to the square of distance.

Ampere's circuital law

The line integral of magnetic field around a closed loop equals the permeability times the net current enclosed by that loop.

Magnetic dipole moment

A vector for a current loop of magnitude NIA, directed normal to the loop by the right-hand rule; torque in a field is mB sinθ.

Faraday's law

The induced EMF in a circuit equals the negative rate of change of magnetic flux through it, with the minus sign expressing Lenz's law.

Self-inductance

The property by which a coil opposes changes in its own current, defined by flux linkage per unit current and measured in henries.

Impedance

The total opposition to alternating current in a series LCR circuit, Z = √(R² + (X_L − X_C)²), measured in ohms.

Displacement current

The fictitious current ε₀ dΦ_E/dt introduced by Maxwell through a region of changing electric flux, which produces a magnetic field like a conduction current.

Electromagnetic wave speed

In vacuum electromagnetic waves travel at c = 1/√(μ₀ε₀) ≈ 3×10⁸ m/s; in a medium of refractive index n the speed is c/n.

Total internal reflection

When light travels from a denser to a rarer medium at an angle exceeding the critical angle, it is entirely reflected back into the denser medium.

Fringe width

In Young's double-slit experiment, the spacing between consecutive bright or dark fringes on the screen, given by β = λD/d.

Brewster's law

At a particular angle of incidence, tanθ_p = n, the reflected light is completely plane polarised with vibrations perpendicular to the plane of incidence.

Stopping potential

The reverse potential that just reduces the photocurrent to zero; it measures the maximum kinetic energy of emitted photoelectrons as eV₀.

de Broglie wavelength

The wavelength associated with a moving particle, λ = h/p, showing matter has wave character confirmed by electron diffraction experiments.

Threshold frequency

The minimum frequency of incident radiation below which no photoelectrons are emitted from a given metal surface, equal to work function divided by Planck's constant.

Bohr radius

The radius of the first allowed electron orbit in hydrogen, approximately 0.53 Å, scaling as n² for higher orbits.

Half-life

The time in which half the radioactive nuclei in a sample decay; it equals 0.693 divided by the decay constant and is independent of sample size.

Mass defect

The difference between the sum of nucleon masses and the actual nuclear mass; multiplied by c² it gives the nuclear binding energy.

Depletion layer

The narrow region around a p–n junction depleted of mobile carriers, containing fixed ions and creating a potential barrier that opposes further diffusion.

Zener breakdown

A reverse-bias phenomenon in heavily doped diodes where a sharp, nearly constant reverse voltage develops across the junction, used for voltage regulation.

Transistor current gain beta

In common-emitter configuration, the ratio of collector current to base current; it relates to alpha by β = α/(1 − α).

Screw gauge least count

The pitch of the screw divided by the number of circular scale divisions, commonly 0.01 mm, added to the main scale reading after zero-error correction.

Potentiometer principle

A steady current through a uniform wire gives a potential drop proportional to length, so unknown EMFs can be compared by their balancing lengths.

Dot product

The scalar product of two vectors, A·B = AB cosθ; it is zero for perpendicular vectors and equals the product of magnitudes for parallel ones.

Percentage error

The absolute error divided by the mean value, multiplied by 100; for a quantity raised to power n the percentage error is multiplied by n.

Dimensional formula

An expression showing which base quantities and powers make up a derived quantity, used to check equation consistency and convert units.

Modulation index

For amplitude modulation, the ratio of message amplitude to carrier amplitude, μ = A_m/A_c; values above one cause overmodulation and distortion.

Sky wave propagation

Radio waves in the 3–30 MHz range reflected by the ionosphere back to Earth, allowing long-distance communication beyond the horizon.