8.1 - 8.4 Flashcards
define current
the rate of flow of charge
define ‘coulomb’
the charge flowing past a point in one second when there is a current of one ampere
what is a charge carrier
particles with charge that move through a material to form an electric current
what is conventional current
a model used to describe current in a circuit. it travels from positive to negative. It’s the direction positive charge carriers would flow.
how does electricity flow in electrolytes
It’s the flow of ions from one electrode to the other. the positive ions are attracted to the cathode and the negative ions to the anode.
how can current be measured
using an ammeter connected in series. it must have an extremely low resistance to reduce there effect on the current.
what is Kirchhoff’s first law
the sum of the currents entering a junction equals the sum of the currents leaving a junction. it’s the conservation of charge
what is number density
the number of free electrons per cubic meter of a material
What’s the average number density of conductors, semiconductors and insulators
conductor: 10^28
semiconductor: 10^17
insulator: <10^9
how fast are charge carriers and why do lights turn on so fast
charge carriers move slowly because they collide with the metal cations as they move. lights turn on instantly because all of the charge carriers in a wire start moving at once
what is the mean drift velocity
the average velocity of electrons as they flow through a wire
whats the relationship between cross-sectional area and mean drift velocity
the cross-sectional area is inversely proportional to mean drift velocity if the current is constant
