Electricity is the energy carried by the charge.
Current is the rate of flow of charge. Measured by ammeter and SI unit is
ampere(A).
Charge is the product of time and current. SI unit is coulomb C.
Basic charge is the charge on an electron and its value is 1.6 x 10-19C. Quantised
mean is fixed so the charge on a particle is quantised. It cannot vary as the
charge is the integral multiple, its the basic component so cannot change.
Number density(n): is the number of free electrons per unit volume. N/V where
N is the number of free electrons and V is the volume per m3.
Conductivity is the conduction of charge. The higher the number density the
higher the conductivity.
Drift velocity: the average velocity of free electrons in a conductor when the
potential difference across it. I=nAQv where n is the number density, A= the are
of cross section of wire,v= the drift velocity,I= current and Q= charge.
Derive the relation of I=nAQv
So I=Q/t and Q=Nq as N=number density and q is the individual charge on an
electron while Q represents the total charge that passes in a specific time.
And as n=N/V so N=nv hence Q=nvq while we know that the wire is a cylindrical
shape so has the volume v = A.l
Hence Q=nAlq
Now remember I=Q/t so becomes I=nAlq/t while we can write it as : A.n.q.l/t so
l/t becomes v as l is the length for which the electrons travel and t is the time in
which they passes it is the same as v=d/t so we have derived I=Anvq
Potential difference(V):
Electron is moving from the positive
terminal
to negative terminal. Voltmeter
measures the potential
difference . energy is provided by the
battery that
is consumed by the resistor.
Charges moves from high potential
to the
Lower potential.
1. Workdone per unit charge across two points.
2. V=W/Q where the SI unit is Volts(V) and is measured by a voltmeter.
3. The voltmeter has a very large resistance so the current cannot pass through it
thats why it is set in parallel.
4. It is workdone by the charge.
Electricity.
