BSEB Inter Physics flashcards
BSEB Inter Physics · Build recall with a focused review session.
32 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 the distance between them, acting along the joining line.
- Gauss's law
- The total electric flux through any closed surface equals the enclosed charge divided by the permittivity of free space, regardless of the surface shape.
- Capacitance
- The ratio of charge stored on either conductor of a capacitor to the potential difference between them; for a parallel plate capacitor it equals ε₀A/d in vacuum.
- Electric dipole moment
- A vector of magnitude equal to charge times separation, directed from negative to positive charge; it determines the torque and field of the dipole.
- Drift velocity
- The small average velocity with which free electrons move opposite the applied field in a conductor, related to current by I = nAev_d.
- Internal resistance
- The resistance within a cell that causes its terminal voltage to fall below its EMF when current is drawn, so V = ε − Ir.
- Wheatstone bridge balance
- A four-resistance network is balanced, with no current through the galvanometer, when the ratio of the two arms on one side equals that on the other.
- Potentiometer principle
- A steady current in a uniform wire gives a potential drop proportional to length, so unknown EMFs can be compared as ratios of balance lengths without drawing current.
- Biot–Savart law
- The magnetic field due to a current element is proportional to current, element length and 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 of free space times the total current enclosed by that loop.
- Cyclotron resonance condition
- A charged particle circulates in a magnetic field with frequency qB/2πm, independent of speed, so a fixed-frequency alternating voltage can repeatedly accelerate it.
- Magnetic dipole moment
- For a current loop it is the product of current and area, directed along the normal; the torque in a field is the cross product of moment and field.
- Lenz's law
- The direction of an induced current is such that its magnetic effect opposes the change in flux that produced it, expressing conservation of energy.
- Self-inductance
- The property by which a coil opposes change of current through it, producing an EMF equal to the inductance times the rate of change of current.
- Resonant frequency of LCR
- The frequency at which inductive and capacitive reactances are equal, giving minimum impedance equal to resistance and maximum current in a series circuit.
- Transformer action
- Mutual induction between two coils on a common core changes voltage in the ratio of turns; an ideal transformer conserves power, so current changes inversely.
- Displacement current
- A changing electric flux acts like a current in producing a magnetic field, introduced by Maxwell to make Ampere's law consistent with charge conservation.
- Total internal reflection
- When light travels from a denser to a rarer medium beyond the critical angle, it is entirely reflected back, which underlies optical fibres and mirages.
- Fringe width
- In Young's double-slit experiment, the spacing between consecutive bright or dark fringes equals wavelength times screen distance divided by slit separation.
- Brewster's law
- At a particular angle of incidence, reflected light is completely polarised; the tangent of that angle equals the refractive index of the reflecting medium.
- Work function
- The minimum energy needed to release an electron from a metal surface; it fixes the threshold frequency below which no photoelectric emission occurs.
- Stopping potential
- The reverse potential that just stops the fastest photoelectrons; multiplied by electron charge it equals maximum kinetic energy and rises linearly with frequency.
- de Broglie wavelength
- Every moving particle has an associated wavelength equal to Planck's constant divided by its momentum, observable for electrons and confirmed by diffraction experiments.
- Bohr quantisation condition
- In a hydrogen atom, electrons occupy orbits in which angular momentum is an integer multiple of h/2π, and radiation occurs only on transitions between orbits.
- Half-life
- The time in which half the nuclei in a radioactive sample decay; after n half-lives the remaining fraction is one over two to the power n.
- Binding energy per nucleon
- The energy released when nucleons combine, divided by their number; it peaks near iron, making fusion favourable for light nuclei and fission for heavy ones.
- Zener diode regulation
- A heavily doped diode operated in reverse breakdown, where voltage stays nearly constant as current changes, so it can stabilise a supply voltage.
- Transistor current gain
- In common-emitter configuration, the ratio of collector current change to base current change, denoted beta, typically tens to hundreds for a small signal transistor.
- Universal logic gates
- NAND and NOR gates, because either one alone can be wired to perform NOT, AND and OR operations, so any logic circuit can be built from it.
- Vernier least count
- The smallest measurement a vernier calliper can read, equal to one main scale division divided by the number of vernier divisions, typically 0.1 mm.
- Modulation index
- For amplitude modulation, the ratio of message amplitude to carrier amplitude; it must not exceed one, or the envelope distorts through overmodulation.
- Sky wave propagation
- Radio waves in the high-frequency range travel to distant receivers by reflection from the ionosphere, useful beyond the line of sight.