Electrical Properties

Question 1

does the 2s electron state break into individual energy bands at a smaller or larger interatomic separtation than 1s

Answer 1

at a larger separation

Question 2

what do electrical properties depend on?

Answer 2

the arrangment of the outermost electrons and how theyre filled with electrons

Question 3

which electrons will be accelerated when an electric field is passed through them

Answer 3

only the ones with an energy greater than the fermi energy

Question 4

what does the electrical conductivity depnend on?

Answer 4

the number of free electrons and the number of holes

Question 5

how do metals access nearby energy states

Answer 5

by thermal fluctuations

Question 6

what is the relationship between the band gap and the electrical conductivity

Answer 6

the larger the gap, the lower the conductivity

Question 7

How can we decrease resistivity (3 ways)

Answer 7

of impurities, temperature, %Cold Work

Question 8

which type of imperfections increase resisitivity (4) for metals

Answer 8

• grain boundaries
• dislocations
• impurity atoms
• vacancies

Question 9

why do imperfections increase resisitivity

Answer 9

because they force the electrons to take a less direct path

Question 10

why does increasing temp increase resistivity

Answer 10

because it causes the atoms to vibrate more, making it harder for the electrons to move through them

Question 11

why does increasing %CW increase resistivity

Answer 11

because it increases dislocation concentration

Question 12

formula for electrical conductivity

Answer 12

1/rho(resistivity)

Question 13

what are the types of charge carriers in insulators and semi conductors?

Answer 13

Free electrons and Holes

Question 14

Describe free electrons:

Answer 14

-have negative charge and are located in the conduction band

Question 15

describe holes:

Answer 15

have positive charges and are located in the valence band

Question 16

for semi-conductors what is the relationship between temperature and electrical conductivity

Answer 16

as T increases, conductivity increases

Question 17

for an intrinsic what is the ratio between number of electrons and the number of holes

Answer 17

they are equal

Question 18

how would we create EXTRINSIC conduction

Answer 18

by adding impurites with different # of valence electrons than the host atom

Question 19

what is the main difference between intrinsic and extrinsic conduction

Answer 19

the number of electrons does not equal the number of holes

Question 20

what are the 2 types of extrinsic conduction and describ

Answer 20

N type and P types
N types: N>P
P type P>N

Question 21

If we have donor impurities what is the case:

Answer 21

N type; negative conductivity by electrons

Question 22

if we have acceptor imupurites what is the case:

Answer 22

P types; positive conductivity by holes

Question 23

How can we control the conductivity

Answer 23

by controlling the concentration of donors/acceptors

Question 24

where is the donor impurity energy level located

Answer 24

just below the conduction band

Question 25

where is the acceptor energy level located

Answer 25

just above the valence band

Question 26

Pure materials have which type of conductivity

Answer 26

intrinsic

Question 27

Acceptors create [blank] and Donors donate [blank]

Answer 27

[holes] and [electrons]

Question 28

why does doping increase the conductivity

Answer 28

because imperfection sizes lower the activation energy to produce free electrons