Chapter 8, Charge And Current

Question 1

Equation for current in terms of charge including units

Answer 1

I = Q(coulombs) / T(seconds)

Question 2

What is the value of the elementary charge e?

Answer 2

e = 1.6x10^-19 C

Question 3

What two things could cause an increase in rate of charge flow?

Answer 3

More electrons passing through a given point (greater cross sectional area)
The same number of electrons electrons moving faster through the wire

Question 4

What is Kirchhoff’s first law?

Answer 4

The sum of the currents into a junction is equal to the sum of the currents leaving the junction

Question 5

How are materials classified by conductivity?

Answer 5

Their number density (number of free electrons per cubic meter)

Question 6

What are the three categories of conductivity of material?

Answer 6

Insulators, semiconductors, conductors

Question 7

What is the equation for current in terms of mean drift velocity?

Answer 7

I = Anev where A is cross sectional area in meters squared and v is velocity in ms

Question 8

How does reducing the cross sectional area of a wire affect the drift velocity if flow of charge remains constant?

Answer 8

The drift velocity increases in the smaller area to compensate