Electrical- Intro

Question 1

Conductivity range for metals, semiconductors and insulators

Answer 1

10^-18 to 10^-6 for insulators
10^-6 to 10^2 for semiconductors
10^2 to 10^6 for metals

Question 2

What is current?

Answer 2

Movement of charged particle within a material under the influence of an electric field or potential difference. What moves could be electrons (electronic conduction), charged ions (ionic conduction), holes (absence of electrons, like a positive charge, occurs in semiconductors and is associated with defects in the structure)

Question 3

Short and long range for how far charged species move readily

Answer 3

Short range is about 1 bond length (semiconductors)

Long range much greater than 1 bond length (metals, electrolytes)

Question 4

Why does a charge move?

Answer 4

Application of difference in electric potential

Question 5

Formula for resistivity

Answer 5

ρ=RA/L

Question 6

What is conductivity?

Answer 6

Symbol σ. Inverse of resistivity (1 over)

Question 7

What is current density?

Answer 7

Symbol J. Current per CSA

Question 8

Electric field gradient

Answer 8

Symbol ε. Voltage per unit distance

Question 9

Formula for current density like Ohms law

Answer 9

J=σε

Question 10

How to minimise power loss (resistive heating) in long conductors

Answer 10

Reduce I or R

Question 11

What is mobility?

Answer 11

Symbol μ. Measure of how easily charges move

Question 12

Formula for conductivity involving mobility

Answer 12

σ=nqμ
n is how many charge carriers there are in given volume
q is the charge of the charge carriers