# Electrical and diffusion current Flashcards

1
Q

Symbol: Q

A

Charges

2
Q

Symbol: t

A

Time

3
Q

Symbol: I / Ix

A

Current

4
Q

Symbol: e

A

Charge of an electron

5
Q

Symbol: n

A

Number density

6
Q

Symbol: A

A

Cross-sectional area

7
Q

Symbol: Vdx / vdx

A

Mean drift velocity

8
Q

Symbol: J / Jx

A

Current density

9
Q

Symbol: μd

A

Drift mobility

10
Q

Symbol: Ex

A

Electric field strength

11
Q

Symbol: σ

A

Conductivity

12
Q

Symbol: De

A

Diffusion coefficient

13
Q

Symbol: x

A

Displacement

14
Q

Symbol: t / ∆t

A

Time

15
Q

Symbol: me

A

Mass of an electron

16
Q

Symbol: τ

A

Scattering time

17
Q

Symbol: N

A

Number of charges / Particles

18
Q

Symbol: V

A

Volume

19
Q

Symbol: a

A

Acceleration

20
Q

Symbol: ρ

A

Resistivity

21
Q

Symbol: R

A

Resistance

22
Q

Symbol: l with regards to resistivity

A

Length

23
Q

Symbol: Γ

A

Particle flux

24
Q

Symbol: l

A

Mean free path

25
Q

What is the number density?

A

This is the number of electrons per unit of volume

26
Q

What is mean drift velocity?

A

The average velocity of particles moving through a wire

27
Q

What is current density?

A

The rate of flow of charge per unit area

28
Q

What is current?

A

The rate of flow of charge

29
Q

What is drift mobility?

A

> The average drift velocity acquired per unit of electric field
A good measure of the quality of a wire

30
Q

What is conductivity?

A

> This is the inverse of resistivity

31
Q

What is the diffusion coefficient?

A

The diffusion coefficient is a measure of how well particles (here electrons) diffuse in a medium, and is the equivalent of conductivity

32
Q

What is the scatter time?

A

The mean time between collisions

33
Q

What is particle flux?

A

Number of particles / (Area × Unit of time)

34
Q

What is the mean free path?

A

This the average distance travelled by particles between collision

35
Q

3 Equations for current

A
```I = dQ/dt
I = Q/t
Ix = enAVdx```
36
Q

What are 4 equations for current density?

A
```J = I/A
J = enVdx
J = enμdE
J = σE```
37
Q

What is the equation to calculate mean drift velocity?

A

Vdx = ( eE / me)τ

38
Q

How is the equation for mean drift velocity calculated?

A
```F = qE = eE
F = MA
eE = me×A => A = eE/me
Vdx = A×∆t
Vdx = (eE/me)τ```
39
Q

What is the equation for resistance in terms of resistivity?

A

R = ρl/A

40
Q

What are 3 equations for conductivity?

A
```σ = 1/ρ
σ = ne^2τ/me
σ = neμd```
41
Q

What are 2 equations for drift mobility?

A
```μd = Vdx/E
μd = eτ/me```