Definitions 2 Flashcards
Brittle materials
Materials which do not undergo plastic deformation. Force is proportional to extension until it breaks
Ductile materials
Materials which undergo plastic deformation after a considerable elastic deformation. Initially force is proportional to extension then a large extension for a small change in force
Elastic deformation
Object returns to its original length (zero extension) when load is removed
Force-extension graph
The area under such a graph is the work done in stretching the material; for the straight-line portion of the graph, it is a measure of the elastic potential energy stored by the material
Hooke’s law
Force/load is proportional to extension/compression if proportionality limit is not exceeded
Plastic deformation
Body does not return to its original shape/length when load is removed
Strain
Extension over original length (ratio); stress is the cause and strain is the effect
Stress
It is the force per uint cross-sectional area required to stretch a material
Ultimate tensile strength
The maximum value of stress that an object can sustain before it breaks
Ultimate tensile stress
The maximum value of stress that an object can sustain before it breaks
Young’s modulus
Ratio of stress to strain
Electric current
It is the amount of charge flowing pass a point per unit time or rate of flow of charged particles
Ohm’s law
The current through a metallic conductor is proportional to the P.D across it provided that its temperature remains constant
Potential difference
The energy converted from electrical to other forms of energy per unit charge that passes through it
Quantised
Charge only exists in discrete amounts of 1.6x10-19 C; charge on carriers is quantised
Resistance
The ratio of P.D over the current for an electrical component
Resistivity
The resistivity of a wire of a particular material is its resistance for unit length
Thermistor
A specific type of resistor, in which, as temperature increases, the magnitude of its resistance decreases and vice versa
E.M.F
The amount of energy converted into electrical energy per unit charge supplied
P.D
The amount of electrical energy converted into other forms of energy per unit charge supplied
Internal resistance
The resistance inherent in a source/cell itself causing some energy to be transferred into other forms to reduce the available voltage for the rest of the circuit
Kirchhoff’s 1st law
The sum of currents into a junction = sum of currents out of junction; from the conservation of charge
Kirchhoff’s 2nd law
The sum of EMFs = sum of PDs around a closed loop/circuit; from the law of conservation of energy
Potentiometer
A variable resistor connected as a potential divider to give a continuously variable output voltage
Potential divider
Series circuits which produce an output voltage as a fraction of its input voltage
The ratio of the output voltage to the input voltage = the ratio of the output resistance over the total resistance
Galvanometer
A component used to detect small changes in electric current; it is a sensitive ammeter
When the needle is not deflected, the current equals zero and the EMFs of the two sources is equal
Kinetic energy of alpha particles
Alpha particles have discrete energies; this is due alpha decay only releases alpha particles and nothing else while decaying into a daughter nucleus
Kinetic energy of beta particles
Beta particles have a continuous range of energies; this is as the energy released in beta decay is shared between the beta particles and neutrinos
Unified atomic mass
1.66x10^-27 kg = the mass of one proton or neutron
1 elementary charge of an electron or proton
+|- 1.6x10^-19 C
One coulomb of charge
6.24x10^18 electrons or protons
Mass and charge of an alpha particle
Mass in u = 4
Charge in e = +2
Mass and charge of beta minus particle
Mass in u = 0.0005
Charge = -1e
Mass and charge of beta plus particle
Mass in u = 0.0005
Charge = +1e
Speed of a beta minus and beta plus particle
> 0.99c (3x10^8ms-1) - beta minus and plus particles have the same speed
Speed of an alpha particle
0.05c
Composition, mass and charge of gamma rays
Composition = electromagnetic waves
Charge and mass = 0
How do you calculate the mass of an element in u?
It’s mass is equal to the sum of its protons and neutrons = nucleon number
How were neutrinos discovered?
One if the first clues of the existence of neutrinos was the fact that beta particles have a continuous range of energies
What happens to a nucleus during alpha decay?
Proton number decreases by 2
Nucleon number decreases by 4
What happens to a nucleus in beta minus decay?
Proton number increases by 1
Nucleon number remains the same
What happens to a nucleus in beta plus decay?
Proton number decreases by 1
Nucleon number remains the same
Equation for the number of charge carriers
Q = ne
Q = total charge transferred
e = 1.6 x 10^-19 (the charge on one electron)
Potential divider equation
V out / V in = R out / R in
Ratio of potential differences = ratio of resistances
Potential divider equation
V out / V in = R out / R in
Ratio of potential differences = ratio of resistances
Potentiometer formula
EMF 1 / L1 = EMF 2 / L2
How to PD related to length?
PD is directly proportional to length
(PD is the output when connected as well potentiometer)
How is resistance related to length?
Resistance is directly proportional to length
