Physics definitions A levels

all the definitions for physics a levels

Electric field

A region of space in which a force acts on a stationary charge

Electric field strength

Electric force per unit positive charge exerted on a test charge placed at that point.

Coulomb’s Law

Electrostatic force between 2 point charges is directly proportional to the product of the charges and inversely proportional to the square of the separation. The direction of the force acts along the line joining the two point charges.

Electric potential

Work done per unit positive charge in bringing a small test charge from infinity to that point.

Equipotential lines

Lines joining points in a field that have the same potential, they meet perpendicular to the electric field lines

Angular displacement

Angle through which an object turns

Angular velocity

Rate of change of angular displacement of a radius that joins the body to the centre of a circle

Kinetic theory of gases

1. No forces of attraction or repulsion between atoms unless they are in collision with each other or the walls of the vessel

2. Gas molecules are in constant, random motion and obey Newton’s laws of motion

3. Time of collisions is negligible compared with time between collisions

Ideal gas

Hypothetical gas that obeys the equation of state (pV=nRT0 for an ideal gas perfectly for all pressure p, volume V, amount of substance, n and temperature T

Thermal equilibrium

When two objects in thermal contact are in thermal equilibrium, there is no net heat transfer between them, they are at same temp

Principle of superposition

When two or more waves of the same type meet at a point at the same time, the displacement of the resultant wave is the vector sum of displacements of individual waves at that point at that time.

Stationary waves

When two progressive waves of the same type that are travelling in opposite directions with the same speed, frequency and amplitude meet, they undergo superposition to form stationary waves

Diffraction

Spreading of waves through a gap or an obstacle

Rayleigh criterion

For the two patterns to be just distinguishable, the central maximum of one must lie on the first minimum of the other

Interference

Two sources need to be coherent, waves produced by the sources have a constant phase difference

Two source

1. Waves must overlap

2. Waves must be coherent

3. Waves must have equal amplitudes

Transverse

Displacement of the particles in the wave are at right angles to the direction of transfer of energy

Longitudinal

Displacement of the particles in the wave are along the direction of transfer fof energy of the wave

What affects the resistance of conductor

1) No. of charge carrying conductors, n → decreases R
2) Thermal vibrations of the lattice structure → Increases R

Electric current

Flow of charged particles

Potential difference

Work done per unit charge when electrical energy is transferred to non electrical energy when the charge passes from one point to another

E.m.f.

Work done per unit charge when non electrical energy is transferred to electrical energy when the charge moves round one complete circuit

Resistance

Ratio of potential difference across the conductor to the current passing through it

Resistivity

Relationship between the dimensions of a specimen of a material and its resistance that is constant at constant temperature, calculated by p = RA/L where R is resistance, A is cross sectional area, L is the length