ch 8 - electric current Flashcards
conventional current
positive to negative
electron movement in a circuit
negative to positive
electrons are the particles that allow a metal to conduct an electrical current
what is a charge carrier
a charged particle that contributes to an electric current - may be electrons, protons, ions
quantised?
a quantity is said to be quantised when it has a definite minimun magnitude and alqays comes in multiple sof that magnitude
what is current
the rate of flow of electric charge past a point
symbol - I
units - A
charge formula
charge = current * time
Q = It
what is a coulomb
one coulomb is the charge that flows past a point in a circuit in a time of 1s when the current is 1A
what is the value of elementary charge
1.6 * 10^-19 C
what is number density?
the number of charge carriers, such as free electrons, per unit volume in a material
what is mean drift velocity
the averga espeed of a collection if charges particles when there is current in a conductor
current in terms of drift velocity formula
I = nAvq OR I = nAve
I = nAvq derivation
no. of electron = n * volume of wire
no. of electron = n * Al
charge of electrons = nAl * e
I = Q/ t soo
I = nAl * e/t
substitute v = 1/t
I = nAve
ooor
I = nAvq
thinner wire =? drift velocity
greater
v proportional to I
v proportional to I / A
v proportional to 1/n
voltage in series and parallel
series - different
parallel - same
current in series and parallel
series - same
parallel - different
what is potential difference between A and B
energy transferred by unit charge as it moves from point A to B
voltage formula
V = change W / change Q
V = IR
what is emf
the energy transferred per unit charge in driving charge round a complete circuit
what is electrical resistance
the ratio potential difference to current, unit = ohm
what is an ohm
the resistance of a component when a potential difference of 1V drives a current on 1A through it
electrical resistance formula
R = V/I
electrical power formulas
. P = VI
. P = I²R
. P = V²/R
W = IVt
