Electricity Flashcards
what is kirchoffs first law?
at any point in an electrical circuit the sum of currents into that point = sum of currents out of that point
what is the mean drift velocity
the average velocity of electrons moving through a wire
mean drift velocity equation
I=Anev I = current in conductor n = number density e = elementary charge v = mean drift velocity
what effect does a thinner wire have on the mean drift velocity
if current is constant then mean drift velocity has to increase as wire gets thinner
what does the ideal ammeter have
zero resistance
what is EMF
electro motive force
describes when work is done on charge carriers
where energy is transferred from other energy forms into electrical energy
what is PD
potential difference
describes when work is done charge carriers
when energy is transferred from electrical energy into other forms of energy
what is ohms law
for a metallic conductor kept at a constant temperature, the current in the wire is directly proportional to the potential difference across it
what is resistivity
an electrical property of a material.
resistance is proportional to length/area. the constant is resistivity
equation for resistivity
R= pl/A
as a material gets hotter what happens to its resistivity
as a material gets hotter, the resistivity increases
what are semiconductors
they have negative temperature coefficients so their resistance drops as thei temperature increases
what are thermistors made of
semiconductors
what is power
the rate of energy transfer
what is kirchoffs second law
the sum of electromotive forces is equal to the sum of pds around a closed loop
