Physics - Definitions

Physics - Definitions Page | 1 Dynamics

Diffraction

Newton’s Second Law

1. 2.

1. 2. 3.

Rate of change of momentum of a body is directly proportional to the resultant force acting on it and changes in the direction of the resultant force.

Waves bending round an obstacle or through an aperture spreading into the region.

Principle of Superposition 1.

When two waves of the same kind are superimposed in space

Newton’s Third Law

2.

the net displacements at any point of space and time

1. 2.

3.

is the vector sum of all individual waves at that point.

If body A exerts a force on body B body B will exert an equal and opposite force on body A

Circular Motion Centripetal Force 1. 2.

The force providing the centripetal acceleration to enable a body to go round in a circle

Gravitational Field & Electric Field Gravitational Field Strength 1.

Gravitational force per unit mass placed at that point.

Electric Field Strength 1.

Electric force per unit positive charge placed at that point

Gravitational Potential 1.

Work done in bringing unit mass from infinity to the point.

Interference

1.

The result of superposing two or more coherent waves.

Current of Electricity Electromotive Force

1. 2.

The amount of energy converted from other forms of energy to electrical energy per unit charge delivered around a complete circuit.

Potential Difference

1. 2.

The amount of energy converted from electrical energy to other forms of energy per unit charge delivered between two points.

Volt

Electric Potential

1.

The potential difference between two points

1.

2. 3.

if one joule of energy is converted per coulomb of charge moved across the points.

Work done in bringing unit positive charge from infinity to the point.

Newton’s Law of Gravitation

Coulomb

1. 2. 3.

1. 2.

Any two bodies attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of their separation.

The quantity of electricity passing a given point when a current of one ampere is maintained for one second.

Magnetic Field Coulomb’s Law Magnetic Flux Density 1. 2. 3.

Any two charged particles exert a force on each other that is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

1. 2. 3.

Force per unit length of conductor per unit current carried placed at right-angles to the magnetic field

Simple Harmonic Motion

Magnetic Flux

Simple Harmonic Motion

1. 2.

1. 2. 3.

Oscillatory motion in which the acceleration is proportional to its displacement and directed towards its equilibrium position.

Damping 1. 2.

Loss of energy caused by dissipative forces such that the amplitude of the system decreases.

Product of the magnetic flux density and the area perpendicular to the field

Tesla 1. 2. 3. 4.

The flux density of a field in which a conductor of length 1m carrying a current of 1A at right-angles to the field experiences a magnetic force of 1N

Electromagnetic Induction Thermal Physics Faraday’s Law of Electromagnetic Induction First Law of Thermodynamics 1. 2. 3.

The increase in the internal energy of a system is equal to the sum of the heat supplied to the system and the work done on the system.

1. 2.

Lenz’s Law

Zeroth Law of Thermodynamics

1.

1. 2.

2.

If two bodies are in thermal equilibrium with a third, they are also in thermal equilibrium with each other.

The magnitude of the induced e.m.f. is proportional to the rate of change of the magnetic flux linkage.

An induced current will flow in a direction that produces a magnetic field which opposes the change in magnetic flux that induced it.

Weber

Superposition

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1.

The magnetic flux passing through a plane surface of 1m2

2.

placed normal to a uniform magnetic field of flux density 1T

2 | Page Alternating Current Root-Mean-Square Current 1. 2.

Equivalent value of a direct current which dissipates heat at the same average rate as the alternating current.

Quantum Physics Work Function Energy 1.

Energy required to release an electron from the surface.

Threshold Frequency 1.

Minimum frequency a photon must have to cause photoelectric emission.

Photoelectric Effect 1. 2. 3.

The phenomenon when electromagnetic radiation of frequency above a certain minimum value falls on the surface of a metal and electrons are emitted.

Lasers and Semiconductors Spontaneous Emission 1. 2.

An atom in an excited state transits to a lower energy state with the result that a photon is emitted.

Stimulated emission 1.

2. 3.

An incoming photon of correct energy could stimulate the transition of the electron from the excited state to the ground state, resulting in the emission of two photons of the same frequency, phase and direction.

Population inversion 1.

Where there are more atoms in the excited state than a lower energy state.

Nuclear Physics Binding Energy 1.

Energy required to split a nucleus apart into its constituent nucleons.

Decay Constant 1.

Fraction of the total number of active nuclei that decay per unit time.

Spontaneous 1.

Occurs without the presence of any external influence

Random 1.

Impossible to predict which particular nucleus will decay at a given time

Activity 1.

Number of decays per unit time.

Half-life 1.

Average time taken for half the number of active nuclei present to decay.