Basics Flashcards
power, voltage, resistance formula
P = V²/R
converting between power and voltage of diff countries
The resistance of the bulb stays constant, so use P = V²/R to figure it out
Electricity
The presence and motion of charged particles
Electric current
flow of charged particles
Electric charge
Fundamental property of the elementary particles that form the basis of matter
What are conductors, insulators and semiconductors?
Classification of solids by their effectiveness in transferring electric charge
Conductors are mostly
Metals
Insulators are mostly
Nonmetal materials
What are semiconductors?
Metalloids with properties in-between/a mixture of those of metals + non-metals
Six elements commonly recognised as metalloids
Boron Silicon Germanium Arsenic Antimony Tellurium
Eg of conductors
copper aluminium silver platinum bronze gold
Eg of insulators
glass rubber plastic air varnish paper wood mica ceramic certain oils
Energy band model of matter
In solids, energy levels form continuous bands of energy rather than discrete energy levels of atoms in isolation, as large no. of atoms are brought together (no. of orbits becomes v large)
Fermi level
Highest energy level that an electron can reach or occupy in a material at absolute zero temperature
Valence band in solids
highest range of electron energies in which electrons are normally present at absolute zero temp
Valence electrons vs conduction electrons
- Valence electrons bound to indiv atoms
- Cond electrons can move freely within atomic lattice of material
Band gap
- Separates valence band and conduction band in insulators and semiconductors
- in metals: no energy gap
One of the laws of electric charge
Like charges repel each other while unlike charges attract each other
Electric charge:
- unit of charge
- symbol
- Coulomb
- C
what is one Coulomb?
Amount of electric charge transported in one second by a constant current of one ampere
Coulomb’s Law
F ∝ Q₁Q₂/r²
Constant of proportionality
1/4πε
what is ε
permitivity of space between charges
permitivity
property of a medium that accounts for its effect on force between the charges
permitivity of free space
-for a vacuum the permitivity is denoted as ε₀
Force between charges formula
(1/4πε)(Q₁Q₂/r²)
Force between charges and sign
- Force is negative and is of attraction if charges are of opposite sign
- Positive force of repulsion if charges are of same sign
Units of permitivity of free space
- Farad per metre (F/m)
- C²/Nm²
Electrostatic lines of force diagrams
Like charges: forces tend to divert charges away from each other
Unlike charges: tend to move towards each other
Electric field
exists in a region of space in which a stationary charge experiences a force
Electric field strength
E, at a point is the force experienced per unit positive charge on a point charge placed at that point
Electric field formula
E = F/Q
F = electric force experienced by a particle of charge +Q
Electric field strength 0 scalar or vector?
Vector
Electric field strength units
N/C
