Describe the motion of electrons in a wire without current.
Random movement in all directions
Describe the motion of electrons in a wire with current.
Random movement in all directions with an overall drift in one direction
Define: Drift Velocity
Average velocity of electrons moving in a wire
How does the drift velocity compare to an electron's actial velocity?
What is an electrons actual speed?
What does the dirft velocity affect?
What does 'I' stand for in I = vAne?
Electric current in A
What does 'v' stand for in I = vAne?
Drift Velocity in m/s
What does 'A' stand for in I = vAne?
Cross-sectional area in m^2
What does 'e' stand for in I = vAne?
The charge on a single electron.
What does 'n' stand for in I = vAne?
Number of charge carriers per m^3
What happens to the current if the number of charge carriers doubles?
What happens to the current if the area of the material doubles?
What happens to the current if the charge carriers' speed doubles?
You get twice the charge in the same time: Twice the current
What happens to the current if the charge carried by each carrier is doubled?
Twice the charge in the same time: Twice the current.
What are the charge carriers in a metal?
Free, mobile electrons (outer shell)
Considereing the number of charge carriers in a metal, would the drift velocity need to be large or small for a high current?
Small, as there are lots of charge carriers so a low drift velocity is needed.
Are metals conductors, semiconductors or insulators?
Describe the amount of charge carriers in a semiconductor.
Fewer than in metal but more than an insulator
Considering the amount of charge carriers in a semiconductor, would the drift velocity need to be greater or smaller to acieve the same current as a conductor?
Drift velocity needs to be greater, as there are fewer charge carriers.
Describe the perfect insulator.
N=0 no charge carriers, therefore there would be no current I = vAne.
Describe a real insulator.
N is a very small number.
What has to happen to ionic crystals to become conductors?
They have to become molten or aqueous, as then there are positive and negative ions which acts as charge carriers.
How do gases become conductors?
If a high enough voltage is applied then electrons get ripped out of their atoms, giving you ions along a path; a spark.