definitions 3 Flashcards
Einstein’s first postulate?
Physics works the same way for all observers, regarldess of their relative motion or inertial frames of reference. Physical behaviour cannot depend on any absolute velocity.
Einstein’s second postulate?
The speed of light, c, is a universal constant. It has the same value, regardless of the motion of the platform from which it is observed. The translation between distance and time units is the same for everybody.
Elastic deformation?
When a material regains its original shape after deformation.
Elastic limit?
The maximum stress at which an object returns to its original shape after the deforming stress is removed.
Electric field?
The region surrounding an electrical charge in which another electrical charge would experience a force.
Electric field strength?
The magnitude and direction of the force on a charge of 1 coulomb at a given point in an electric field. Symbol, E. Units N/C or V/M
Electric force constant, k?
The constant of proportionality, k, in coulombs law.
Electric potential?
The electrical energy per coulomb of a charge at a specific point, being the work done to move 1C from infinity to the place in question. Measured in V or J/C
Electrical conductivity, σ?
A constant for electrical conductors given by the equation:
G =σA/L
Electrical permittivity of free space?
A fundamental property of free space, ε0, related to the electric force constant, k, given by:
k=1/(4πε)
Electrical resistivity, ρ ?
A constant for electrical conductors given by the equation:
R= (ρL)/A
Electron?
A fundamental particle, a lepton of -1.6*10^-19 C
Electronvolt(eV)?
A practical measure of energy used in atomic and nuclear physics, given by the energy gained by an electron falling through a p.d. of 1V, where one eV is 1.6*10^-19 J.
Energy?
A measure of the capacity of a body or system for doing work.
Energy level?
Confined quantum objects, such as electrons in an atom, exist in discrete quantum states each with a definite energy. This term refers to the energy of one or more such quantum states. (Different states can have the same energy)
Energy transferred thermally?
Energy transfer associated with temperature change. E.g. frictional work can raise the temp of a moving object.
Equilibrium position?
The position of an oscillator in which no net force is acting.
Equipotential surface?
A continual surface joining points of the same potential in a 3D field. E.g grav or electric
Exponential?
A process in which the rate of change of a quantity is proportional to the value of the quantity.
Faraday’s law of electromagnetic induction?
The induced emf,ε , is proportional to negative rate of change of flux.
ε= -d(NΦ)/dt
First law of thermodynamics?
The change in internal energy, delta U is equal to the sum of the work done on a system and the energy transferred thermally into it.
ΔU = W + Q
Flux linkage?
Number of coils * Flux through one coil. Measured in Weber (Wb).
Focal length?
The distance from the centre of a thin lense to the focal point.
Focal point (focus)?
The point where light from a very long distance along the axis of a converging lens is brought to a focus by the lens. This point is also called the focus.
Force constant?
The ratio of force/extension for an elastic specimen.
Forced oscillation?
An oscillation driven by the action of a periodic driving force.
Fracture?
When an object breaks into two or more pieces when placed under pressure.
Fracture stress?
The stress at which fracture occurs. Fracture stress of a material under tension is often called it’s tensile strength.
Free oscillator?
An oscillation due to a restoring force, without any damping or driving forces.
Frequency?
For simple harmonic oscillators, the number of complete oscillations in unit time.
