Engr 54 Electrical Properties

Front 1

What is conductivity?

Back 1

This variable measures ease at which current flows through a material. It depends on the number of charge carriersds

Front 2

What is a metallic bond?

Back 2

In this bond free electrons wander throughout material.

Front 3

What is applying a current?

Back 3

This action causes electrons on a metal to move in the direction opposite the electric field.

Front 4

What are mechanical properties?

Back 4

These properties are strength, hardness and ductility and depend on atomic movements (ex. dislocations.)

Front 5

What are electrical properties?

Back 5

These properties depend on the movement of small charged particles (electrons, ion) in atomic structures.

Front 6

What is resistivity?

Back 6

This property is independent of material geometry, is constant at a particular temperature and measures the resistance particlular material has to current flow.

Front 7

What is conductitiy?

Back 7

This property measures the ease with which current flows through a material. It is dependent on the number of charge carriers, the amount of charge per carrier and the mobility of each character.

Front 8

What is mobility?

Back 8

This property is affected by crystal defects and thermal vibrations (anything that scatters electrons.)

Front 9

As temperature increases the resistivity of metal increases because the number of collions between conduction electrons and atoms increases (mobility decreases.)

Back 9

What are the affects on resistivity when a metal is heated?

Front 10

As temperature increases the resistivity of ceramics and semiconductors increases.

Back 10

What are the affects on resistivity when ceramics and semiconductuors are heated?

Front 11

Resistivity increases becauses distortion in the lattice impedes mobility of charge carriers.

Back 11

What are the affects of resistivity when a material is alloyed with a solid solution?

Front 12

Resistivity increases because becauses dislocations aid in electron scattering (decreases mobility.)

Back 12

What are the affects of resistivity when a material is plastically deformed (cold worked?)

Front 13

What is an electron hole?

Back 13

This carrier is created when an electron jumps from ion to ion leaving behind a hole.

Front 14

What are positive and negative ions?

Back 14

These carriers occur when an ion jumps from one lattice position to another. This occurence is made possible by vacancies.

Front 15

What is the band model?

Back 15

This model is used to determine electrical properties based on quantum mechanics.

Front 16

What is applying voltage?

Back 16

This action excites electrons from lower energy states to higher energy states allowing them to act as charge carriers.

Front 17

What is the valence band?

Back 17

This band is filled and has highest occupied energy levels.

Front 18

What is the conduction band?

Back 18

This band is empty and has the lowest unoccupied energy levels.

Front 19

What is fermi energy?

Back 19

This energy level is that of the highest filled state. Only electrons with energy levels above it participate in conduction.

Front 20

What is an insulator?

Back 20

This material has a full valence band. Its electrons must be excited to the conduction band.

Front 21

What is an energy gap?

Back 21

This energy level is required to excite an electron from the valence band to the conduction band (where it can act as a charge carrier.)

Front 22

electric field (voltage,) electromagnetic radiation, heat and magnetic fields

Back 22

What helps an electron jump the energy gap?

Front 23

What is an intrinsic semiconductor?

Back 23

This material has only conduction band and valence band that are involved in charge transit. Each electron that jumps to the conduction band leaves an electron hole in the valence band.

Front 24

What is an extrinsic semiconductor?

Back 24

This material has conduction characteristics due to a contronlled presence of impurity atoms (doping.)

Front 25

What is an n-type extrinsic semiconductor?

Back 25

This material has negatively charged carriers by the addition of Group V elements (like P, As, Sb) to Si or Ge. The bond leaves a free electron from the added to element to move to the conduction band without creating a hole.

Front 26

What is a donor?

Back 26

This impurity atom donates an electron to the conduction band.

Front 27

What is a p-type extrinsic semiconductor?

Back 27

This material is composed of Si or Ge with an addition of Group III elements (like B or Al) that allow for positively charged carriers by creating a hole from electron deficient bonding.

Front 28

What is an acceptor?

Back 28

This impurity atom accepts electrons.