4.1 Charge and current

Question 1

What is electric current

Answer 1

The rate of flow of charge

It is measured in Amps

Question 2

Give the symbol equation relating charge current and time

Answer 2

Q = It 
charge = current x time

Question 3

In electricity what does ‘e’ represent?

What are the units of ‘e’?

Answer 3

e is the elementary charge (proton has a charge of +e an electron has charge -e)
units are coloumb

Question 4

Give two examples of possible charge carriers

Answer 4

Electrons - in metals

Ions - in electrolytes

Question 5

True or false

Current flows from negative to positive

Answer 5

False
Conventional current is the flow of positive charge - it is in the opposite direction to the movement of the electrons in the circuit

Question 6

How can you measure the current in a circuit?

Answer 6

You can measure the current in a circuit with an ammeter connected in series the component

Question 7

What is Kirchhoff’s first law

Answer 7

All of the current going into a junction is equal to the current leaving the junction

Charge is conserved

Question 8

What is meant by mean drift velocity

Answer 8

the average velocity of the charge carriers due to the applied electric field
It has to be an average because they’re often moving randomly in all directions

Question 9

What equation uses the drift velocity to calculate current?

Answer 9

I = Anev

Question 10

What are the units of ‘number density of charge carriers’?

Answer 10

m^-3

Question 11

Put conductors semiconductors and insulators in order from highest ‘n’ to lowest

Answer 11

conductors
semiconductors
insulators