Einstein photoelectric equation – the maximum kinetic energy of the photoelectrons is the difference between the energy of the incident photon and the minimum energy necessary to free an electron (see equation 27.5)

Elastic collision – a collision in which energy is conserved

Elastic potential energy – energy stored in an elastic object (like a spring) by either stretching or compressing it

Electric charge – the source of the electric force of attraction or repulsion

Electric circuit – a complete (unbroken) conducting path for electric current

Electric current – the rate at which electric charge passes through a conductor (see equation 18.1)

Electric dipole – two equal but opposite charges separated by a fixed distance

Electric field – the electric force per unit charge exerted on a small positive test charge

Electric flux– the number of field lines that pass through a given surface (see figure 16.19)

Electric motor – an apparatus that turns electrical energy into mechanical energy

Electric potential – - ratio of the work done by an external force in moving a charge from one point to another divided by the magnitude of the charge

Electric potential difference – ratio of the work done by an external force in moving a charge from one point to another divided by the magnitude of the charge Electrical conductivity - a measure of the degree to which an applied field can produce a current density in a material

Electrolysis– the process of sending an electric current through a compound in order to separate it into its constituent components

Electromagnetic waves – electric and magnetic fields that radiate in the form of waves from an oscillating electric charge

Electron capture – the decay process in which the nucleus absorbs an orbital electron from the atom

Electrons – small, negatively charged atomic particles

Electromotive force (emf) – the potential difference that appears between the terminals of a battery when no current is present

Electron volt – a unit of energy , 1.6 x 10^-19 Joules (see equations 17.8 and 27.7)

Electrons – small, negatively charged particles

Electrostatics – the study of electrical charges at rest

Elementary charge – magnitude of the smallest charge found on an electron or proton, represented by e

Elementary particles – (sometimes called fundamental particles) refer to atomic structure, specifically proton, neutron, electron, and photon

Energy – the ability to do work

Energy-level diagram- a representation of the allowed orbits in terms of their energy (see figure 27.14)

Entropy – a measure of how much energy or heat is unavailable for conversion into work (see equation 13.7)

Equation of continuity – the rate of flow of a constant density fluid does not change even if the cross section of the enclosure (pipe) changes

Equation of state – an equation that links the pressure, volume, and temperature of a sample of matter

Equilibrium – the rate of flow of a constant density fluid does not change even if the cross section of the enclosure (pipe) changes

Equipotential surface – any surface for which all points are at the same electric potential

Escape speed – the minimum initial upward speed necessary for the object not to fall back to Earth

Exclusion principle – states that no two electrons in an atom may occupy the same quantum space; that is, no two electrons in an atom may have the same four quantum numbers

Eyepiece – in a compound microscope, the lens through which one looks (see ocular)