# Unit 1 Definitions ## Unit 1 Definitions

Current Rate of flow of charge

Potential Difference The energy transferred when unit charge passes between two points

Volt 1 Volt = 1 Joule/Coulomb

Ohm's Law Current is proportional to p.d. (V) provided that the temperature remains constant

Power Rate of energy transfer

Kirchoff's 1st Law Conservation of charge, sum of the current at a junction is zero

Kirchoff's 2nd Law Conservation of energy, sum of the voltage around a closed circuit is zero

EMF The p.d. across the source when no current flows

Internal Resistance Energy transferred within a cell as charge flows through it

Peak Value Maximum displacement from the zero line, it is given the symbol Io or Vo

Peak to Peak Value Maximum displacement across both directions (+ and -)

Time Period This is the time for one complete cycle, it is given the symbol T

Frequency Number of cycles (complete waves) per second, measured in Hz (Hertz)

RMS Value Root mean square value is the effective d.c. value that would produce the same heating effect in a resistor

Proton Positive constituent of an atom's nucleus

Neutron Neutral constituent of an atom's nucleus

Electron Negatively charged particle orbiting the nucleus

Atomic/Proton Number Number of protons in the nucleus

Nucleon/Mass Number Number of protons and neutrons in the nucleus

Isotope Element with the same proton number but a different neutron number

Antimatter Mirror image of a particle with identical mass but opposite charge and other quantum properties

Annihilation Conservation of mass to energy - particle and antiparticle are converted into a pair of protons

Pair Production A high energy photon is converted into a a pair of particles

Strong Force Force experienced by hadrons (baryons and measons)

Weak Force Force experienced by leptons and hadrons, responsible for changes to quark composition

Electromagnetic Force Force experienced by charged particles

Gravity Force experienced by all particles with mass

Fundamental Particles Can't be broken down into smaller particles (e.g. Leptons)

Leptons Electron, muon, tau (Q=-1 for all), electron neutrino, muon neutrino, tau neutrino and their anti-particles

Hadrons Baryons Have 3 quarks and anti-baryons have 3 antiquarks. Measons have a quark and anti-quark pair.

Photoelectric Effect Electrons are emmited from the surface of a mental when the frequency of the light is above the threshold value

Threshold Frequency The minimum frequency of light needed to cause emission of an electron from a metal

Work Function The energy needed to remove an electron from the surface of a metal

Electronvolt Amount of energy gained by an electron accelerated through a p.d. of 1 volt

Excitation An electron moves up an energy level

Ionisation Electron becomes free from the atom after "escaping" the highest energy level

Wave-Particle Duality The ability for waves to behave like particles and particles to behave like waves

Wave Nature of Particles Electron Diffraction

Particle Nature of Waves Photoelectric Effect

deBroglie Wavelength A particle of momentum should have an associated wavelength Permissions in this forum:
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