Conductance

Question 1

How conduction occurs

Answer 1

by promoting electrons into conducting states, that starts right above the Fermi level

Question 2

Conducting states and valence band

Answer 2

separated from valence band by an infinitesimal amount

Question 3

Electric current

Answer 3

-Amount of charge per unit time that passes through a plane that passes completely through the conductor

Question 4

Current formula (definition of current)

Answer 4

i = dq/dt

Question 5

SI units for current

Answer 5

Coulomb per second (C/s),

called an ampere (A)

Question 6

direction of current

Answer 6

-current arrow drawn in direction in which positive charge carriers would move

Question 7

actual charge carriers

Answer 7

• negative

- move in opposite direction of current

Question 8

direction of conventional current

Answer 8

-always from a point of higher potential toward a point of lower potential, ie from positive toward negative terminal

Question 9

When conductor has no current through it

Answer 9

• conduction electrons move randomly

- no net motion in any direction

Question 10

Drift speed

Answer 10

• when conductor has current through it,
• electrons still move randomly,
• but tend to drift w/ a drift speed v𝒹

Question 11

drift speed direction

Answer 11

-in direction opposite that of applied electric field that causes current

Question 12

drift speed formula

Answer 12

i = Nₑ(v𝒹)(Ae)

Ne = number of conduction electrons per cubic meter

Question 13

resistance

Answer 13

-ratio of voltage applied across a piece of material to the current through the material

Question 14

resistance formula

Answer 14

R = V/I

Question 15

SI unit of resistance

Answer 15

Volt/ampere (V/A)
also called
ohm (Ω)

Question 16

resistivity

Answer 16

defined as ρ = E/J

J = current density = I/A (amps/m²)

Question 17

unit of resistivity

Answer 17

ohm-metre (Ωm)

Question 18

conductivity of a material

Answer 18

σ, the reciprocal of resistivity

Question 19

conductivity formula

Answer 19

σ = 1/ρ

Question 20

what is conductivity of a material proportional to?

Answer 20

proportional to number of free electrons and electron mobility

σ = Nₑ |e| μ

Ne = number of “free”/conduction electrons per m³

|e| = absolute charge on a free electron

μ = electron mobility

Question 21

|e|

Answer 21

1.609 x 10⁻¹⁹ C

Question 22

μ unit

Answer 22

m²V⁻¹s⁻¹

Question 23

what resistivity of material depends on

Answer 23

temperature

Question 24

temperature coefficient of resistivity

Answer 24

has the unit of reciprocal temperature

used in:
ρ = ρ₀[1 + α(T - T₀)]

Question 25

conductance

Answer 25

the reciprocal of resistance

Question 26

Conductance formula

Answer 26

G = I/V = 1/R

Question 27

Conductance unit

Answer 27

the siemens (S)

= amps/volts = 1/Ω

Question 28

Ohm’s law

Answer 28

an assertion that current through a device is always directly proportional to potential difference applied to device

Question 29

Ohm’s law formula

Answer 29

I = V/R

Question 30

ohmic material

Answer 30

type of material that obeys Ohm’s law

Question 31

non-ohmic material

Answer 31

type of material which does not obey Ohm’s law

Question 32

when a conducting device obeys Ohm’s law

Answer 32

-when resistance of the device is independent of the magnitude + polarity of the applied potential difference

Question 33

when a conducting material obeys Ohm’s law

Answer 33

-when the resistivity of the material is independent of the magnitude + direction of applied electric field

Question 34

resistance formula and resistivity

Answer 34

R = ρl/A

where l = length, A = area

Question 35

Work done on electron by a force F in moving electron through a small distance 𝛿x (i think this is dx?)

Answer 35

𝑊 = 𝐹𝛿x

Question 36

what is power equal to?

Answer 36

equal to rate of doing work

Question 37

Power formula

Answer 37

Pₑ = F𝛿x/𝛿t

Question 38

resistors

Answer 38

-devices used in circuits to provide resistance of a specified value