Ch 18 - Electrical Properties

Question 1

Describe conduction and electron transport in metals

Answer 1

• empty energy states are adjacent to filled states

- thermal energy excites e- into empty higher energy states

Question 2

What are the two types of band structures for metals?

Answer 2

• partially filled band

- empty band that overlaps filled band

Question 3

What is the relationship between insulators and band gap?

Answer 3

• wider band gap (>2eV)

- few e- excited across band gap

Question 4

What is the relationship between semiconductors and band gap?

Answer 4

-narrow band gap(

Question 5

What is the influence of impurities on resistivity in metals?

Answer 5

presence of imperfections increases resitivity

Question 6

What is the influence of temperature on resistivity in metals?

Answer 6

resistivity increases with temp

Question 7

Define a free electron

Answer 7

• negative charge
• in conduction band
• e charge carrier

Question 8

Define a hole

Answer 8

• e charge carrier
• positive charge
• vacant electron state in the valence band

Question 9

What is a valence band?

Answer 9

completely full outermost band

Question 10

What is a conduction band?

Answer 10

empty outermost band

Question 11

What is an energy band gap?

Answer 11

space between valence and conduction bands

Question 12

What is intrinsic conduction?

Answer 12

electrons equal to # holes

Question 13

What is extrinsic conduction?

Answer 13

• electrical behavior is determined by presence of impurities that introduce excess electrons or holes
• # electrons not equal to # holes

Question 14

Describe the MOSFET

Answer 14

• integrated circuit
• reduce distance between source and grain
• reduce SiO2 insulating layer thickness

Question 15

What is a diode?

Answer 15

electronic device that allows the current to flow in only one direction

Question 16

What is a rectifying junction?

Answer 16

single piece of semiconductor that’s doped to be n-type on one side and p-type on the other

Question 17

What is a forward bias?

Answer 17

• carriers flow through p-type and n-type regions
• holes and e- recombine at p-n junction
• current flows

Question 18

What is a reverse bias?

Answer 18

• carriers flow away from p-n junction
• junction region depleted of carriers
• little current flow

Question 19

What does a p-n rectifying junction do?

Answer 19

allows flow of e- in one direction only

Question 20

What is a junction transistor?

Answer 20

• composed of two p-n junctions arranged back to back

- one junction becomes forward bias, the other becomes reverse