Conduction of electricity

Question 1

Define electric current (I) <– that is an i

Answer 1

A flow of charge
- An SI quantity
- Measured in amperes (A)
- A vector quantity

Question 2

Define electric charge (Q or q)

Answer 2

Current x time
- Measured on coulombs
- A scalar quantity

Question 3

Define coulomb (C)

Answer 3

One coulomb is the total charge supplied by a current of one Ampere in a time of one second

Question 4

Which direction is conventional current?

Answer 4

From positive to negative

Question 5

Which direction is electron flow?

Answer 5

From negative to positive

Question 6

How do we know electron flow is from negative to positive?

Answer 6

Current is the flow of negative free electrons, positive metal ions don’t move

Question 7

Equation for charge? (C)/Q?

Answer 7

Q = I x t
charge = current x time

Question 8

Equation for number of electrons?

Answer 8

Total charge in circuit/Charge of an electron

Question 9

What is drift velocity?

Answer 9

The average speed at which electrons travel in a conductor when subjected in an electric field

Question 10

How to derive I=nAve? (drift velocity)

Step 1

Answer 10

Draw diagram of wire 3D shape:
- Gain area = A
- Gain length = L (vt aka speed x time)
- Gain drift velocity = V
- Gain number of free electrons = n

Question 11

How to derive I=nAve? (drift velocity)

Step 2

Answer 11

Length = v x t
Drift velocity x time

Question 12

How to derive I=nAve? (drift velocity)

Step 3

Answer 12

Volume = A x L = Avt

(vt is the length)

Question 13

How to derive I=nAve? (drift velocity)

Step 4

Answer 13

Number of electrons = Avtn

Question 14

How to derive I=nAve? (drift velocity)

Step 5

Answer 14

Charge in wire = number of electrons x electron charge
Avtne

Question 15

How to derive I=nAve? (drift velocity)

Step 6

Answer 15

I = Q/t = Avtne/t = Avne = nAve

Question 16

How to find drift velocity from I=nAve?

Answer 16

V = I/nAe

Question 17

Explain drift velocity in conductors? (metals)

Answer 17

Conductors have very high electron density = good conductor

Question 18

Explain drift velocity in insulators? (rubber, plastic)

Answer 18

Insulators have much lower electron density (have 1 electron free to move) = cannot conduct

Question 19

Explain drift velocity in semiconductors? (silicon, germanium)

Answer 19

Semiconductors’ electron density lies between conductors and insulators.
However, when it’s hotter, electron density high
When colder, electron density low.

Question 20

U need questions for a topic like this

Also consider answering the questions in the booklet

Answer 20

Applied knowledge….

It’s all about consistency