# 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