ILTS Science: Physics (243) flashcards

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

Independent variable

The variable the experimenter deliberately changes or manipulates; it is plotted on the x-axis when testing its effect on a measured outcome.

Control group

In an experiment, the group that does not receive the treatment and is used as a baseline for comparison to isolate the treatment effect.

Accuracy versus precision

Accuracy is closeness to the accepted value, while precision is repeatability among measurements; a result can be precise but inaccurate due to systematic error.

Percent error

A measure of deviation from an accepted value, calculated as the absolute difference between measured and accepted values divided by the accepted value, then multiplied by 100.

Scientific theory

A well-tested, broad explanation of natural phenomena supported by extensive evidence; it explains why patterns occur and can be revised when new evidence emerges.

Newton's second law

The net force on an object equals its mass times acceleration (Fnet = ma); acceleration is in the direction of the net force and inversely proportional to mass.

Conservation of momentum

In a closed system with no net external impulse, total momentum before an interaction equals total momentum after; it applies to elastic and inelastic collisions.

Centripetal acceleration

Acceleration of an object moving in a circle at constant speed, directed toward the center with magnitude v squared divided by radius; it changes direction, not speed.

Work-energy theorem

The net work done on an object equals its change in kinetic energy; positive net work speeds it up, while negative net work slows it down.

Elastic collision

A collision in which total kinetic energy and total momentum are both conserved; objects bounce apart without lasting deformation or thermal energy loss.

Torque

A rotational effect caused by a force acting at a distance from a pivot, equal to r F sine theta; it depends on force, lever arm, and angle.

Ohm's law

For a metallic conductor at constant temperature, current is directly proportional to potential difference and inversely proportional to resistance: V = IR.

Series circuit rules

In a series circuit, current is the same through every component, voltages add, and total resistance equals the sum of individual resistances.

Parallel circuit rules

In a parallel circuit, voltage is the same across each branch, currents add, and total resistance is found from the reciprocal sum of branch resistances.

Faraday's law

A changing magnetic flux through a coil induces an electromotive force equal to the negative number of turns times the rate of flux change with time.

Lenz's law

An induced current flows in a direction that creates a magnetic field opposing the change in magnetic flux that produced it, conserving energy.

Capacitance

The ability of a system to store charge per unit potential difference, C = Q/V; for parallel plates, capacitance increases with plate area and decreases with separation.

Wave equation

Wave speed equals frequency multiplied by wavelength (v = f lambda); frequency is set by the source, while speed and wavelength depend on the medium.

Snell's law

For light crossing an interface, n1 sine theta1 equals n2 sine theta2; light bends toward the normal when entering a higher-index medium and away when exiting.

Total internal reflection

Occurs when light travels from a higher to lower refractive index medium at an angle exceeding the critical angle, so no refracted ray emerges.

Thin lens equation

Relates focal length, object distance, and image distance: 1/f = 1/do + 1/di; magnification is m = -di/do with sign conventions.

Doppler effect

The observed frequency shifts higher when source and observer approach and lower when they recede; the shift depends on relative motion through the medium.

First law of thermodynamics

The change in internal energy of a system equals heat added to the system minus work done by the system: ΔU = Q - W.

Specific heat capacity

The heat required to raise one unit mass of a substance by one degree Celsius or kelvin, used in Q = mcΔT; water's value is unusually high.

Latent heat

Heat absorbed or released during a phase change at constant temperature, calculated as Q = mL; it changes potential energy between particles, not temperature.

Carnot efficiency

The maximum theoretical efficiency of a heat engine operating between hot and cold reservoirs: 1 minus the cold absolute temperature divided by the hot absolute temperature.

Ideal gas law

Relates pressure, volume, amount, and absolute temperature of an ideal gas: PV = nRT, where R is the universal gas constant.

Photoelectric effect

Emission of electrons from a metal when light exceeds a threshold frequency; it demonstrates that light delivers energy in discrete photons.

de Broglie wavelength

The wavelength associated with a particle, equal to Planck's constant divided by its momentum (λ = h/p); it explains electron diffraction.

Half-life

The time required for half of the radioactive nuclei in a sample to decay; after n half-lives, the fraction remaining is one-half raised to n.

Mass-energy equivalence

Mass and energy are interchangeable according to E = mc squared; a small mass defect corresponds to a large energy release in nuclear reactions.

Heisenberg uncertainty principle

It is impossible to simultaneously know a particle's exact position and momentum; the product of their uncertainties is at least Planck's constant divided by four pi.