# Drift Velocity

## 25 terms

### 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

Much slower

1000000m/s

The current

vAne

### 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

It doubles

It 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.

Conductors.

### 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.