Chapter 4 Elec, Waves, Quantum Flashcards
Equation linking current charge and time?
I=delta Q/ delta t
Electric charge is measured in
coulombs (C)
Elementary charge is
1.6 x 10^-19
Charges of electrons, protons and neutrons
Electron - -e
Proton - +e
Neutron - 0
Equation linking total charge number of electrons and elementary charge
Q=ne
Define electric current
Rate of flow of charge
What are the charge carriers in solutions?
Ions
Conventional current flows from
The positive terminal towards the negative terminal
Electrons travel from
The negative terminal towards the positive terminal
Ammeters are placed in
Series
The conservation of charge states
Electrical charge can neither be created or destroyed
What is Kirchoff’s first law?
The sum of the currents entering any point in a circuit is equal to the sum of the currents leaving that same point
Number density is
The number of free electrons per cubic metre of material
Equation linking current, cross sectional area, number density, elementary charge and mean drift velocity
I=nAve
What effect does a greater cross sectional area have on drift velocity?
Decreases (if constant current)
Three equations for calculating power
P=w/t
P=IV
P=I^2R
P=v^2/R
How many joules are in a kWh?
3.6 x 10^6
Define the volt?
The pd when 1 joule of energy is transferred per coulomb
Voltmeters are connected in
parallel
What is thermionic emission?
The emission of electrons through the action of heat
In an electron gun the greater the accelerating pd
the energy is transferred to the electrons so the faster they move
Define resistance
The ratio of pd to current across the component
Define the Ohm
Resistance when apd of 1v is produce by an ampere of current
What is Ohm’s law?
For a metallic conductor kept at constant temperature, the pd across the component is directly proportional to the current
A photon is
a quantum of electromagnetic energy
What are the two equations for the energy of a photon?
E=hf
E=hc/lambda
Define the electron volt
the energy transferred to or from an electron when it passes though a pd of one volt
Evidence for the wave nature of light includes:
interference and diffraction
Evidence for the particulate nature of light includes
the photoelectric effect
Work function is defined as
the minimum energy needed to remove a single electron from the surface of a particular metal
Threshold frequency is defined as
the minimum frequency of the EM radiation that will cause the emission of an electron from the surface of a particular metal
Which quantity is conserved when a photon interacts with an electron is
energy
The number of electrons emitted from a metal surface is proportional to
intensity (provided the frequency is above the threshold frequency)
Evidence for the wave nature of electrons includes
electron diffraction
