WBBSE Madhyamik Physical Science flashcards

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

Scalar quantity

A scalar quantity has magnitude only and no direction. Mass, distance, speed and time are scalars, while displacement and velocity are vectors.

Average velocity

Average velocity equals net displacement divided by total time. It is a vector, so its sign depends on the chosen positive direction.

Uniform acceleration equations

For constant acceleration a, v = u + at, s = ut + one half at squared, and v squared = u squared + two as, where u is initial velocity.

Vernier least count

The vernier least count is one main-scale division minus one vernier-scale division. For a typical vernier, it is 0.1 mm or 0.01 cm.

Newton's second law

The net force on a body equals its mass times acceleration, F = ma. The acceleration has the same direction as the net force.

Work done by force

Work is force times displacement times cosine of the angle between them. It is zero when force is perpendicular to displacement and negative when opposed.

Kinetic energy

The kinetic energy of a moving body is one half times mass times speed squared. It is a scalar and measured in joules.

Conservation of mechanical energy

In the absence of friction and other non-conservative forces, the sum of kinetic and potential energy remains constant during motion.

Specific heat capacity

Specific heat capacity is the heat needed to raise one kilogram of a substance by one kelvin. Water has a high value, about 4200 joules per kilogram kelvin.

Latent heat

Latent heat is the heat absorbed or released during a change of state at constant temperature. For melting ice it is about 334 joules per gram.

Anomalous expansion of water

Between zero and four degrees Celsius, water contracts on heating and expands on cooling. Water therefore has maximum density at four degrees Celsius.

Newton's law of cooling

The rate of heat loss from a body is proportional to the temperature difference between the body and its surroundings, for small differences.

Wave speed relation

For a wave, speed equals frequency times wavelength. Frequency is measured in hertz and wavelength in metres, so speed is in metres per second.

Echo distance

For an echo, total distance travelled by sound is twice the distance to the reflector. Thus distance equals speed times echo time divided by two.

Pitch and loudness

Pitch depends on the frequency of a sound wave; higher frequency gives higher pitch. Loudness depends on amplitude, and quality depends on the waveform.

Laws of reflection

The incident ray, reflected ray and normal at the point of incidence lie in the same plane, and the angle of incidence equals the angle of reflection.

Snell's law

For light crossing between two media, the refractive index of the second relative to the first equals sine of incidence angle divided by sine of refraction angle.

Critical angle

The critical angle is the incidence angle in the denser medium for which the refracted ray grazes the boundary. Its sine equals the reciprocal of refractive index.

Lens power

Lens power is the reciprocal of focal length in metres. It is measured in dioptres; a convex lens has positive power and a concave lens negative power.

Ohm's law

At constant temperature, the current through a conductor is directly proportional to the potential difference across it, so V equals I times R.

Resistance formula

The resistance of a uniform conductor equals resistivity times length divided by cross-sectional area. Longer wires have more resistance; thicker wires have less.

Series circuit

In a series circuit, the same current flows through each component. Total resistance is the sum of individual resistances, and total voltage divides among components.

Fleming's right-hand rule

It gives the direction of induced current when a conductor moves in a magnetic field: thumb is motion, first finger field, second finger induced current, mutually perpendicular.

Avogadro number

One mole of any substance contains 6.022 times ten to the power 23 particles. This number is used to convert between particle count and amount in moles.

Molar volume at STP

At standard temperature and pressure, one mole of an ideal gas occupies about 22.4 litres. This value links gas volume to moles in calculations.

Combined gas law

For a fixed amount of ideal gas, pressure times volume divided by absolute temperature is constant. This combines Boyle's and Charles's laws.

Atomic number

Atomic number is the number of protons in an atom's nucleus. It identifies the element and, in a neutral atom, equals the number of electrons.

Ionic bond

An ionic bond forms by transfer of electrons from a metal atom to a non-metal atom. The resulting oppositely charged ions attract electrostatically, as in sodium chloride.

Periodic table group

A group is a vertical column of the periodic table. Elements in one group have the same number of valence electrons and similar chemical properties.

Reactivity series

Metals arranged in decreasing chemical reactivity form the reactivity series. A metal higher in the series displaces a lower metal from its salt solution.

Electrolysis

Electrolysis is decomposition of an electrolyte by electric current. Oxidation occurs at the anode and reduction at the cathode; ions move to oppositely charged electrodes.

Alkane general formula

Alkanes are saturated hydrocarbons with only single carbon-carbon bonds. Their general formula is C n H two n plus two, as in methane and ethane.