Chapter 8

Question 1

Electric ucrruent

Answer 1

Defined as the amount of charge that passes a point in a j it do time

Rate of flow of charge , units amps /Cs-1

Question 2

Elementary charge?

What can carry charge

Answer 2

1.6x10-19

Proton has +1e and electron -1e, these are relative charged however

Anything that is a CHARGE CARRIER, so ions too, electrons etc

Question 3

How many electrons in one column

Answer 3

If 2 Collin has charge 1mand electron 1.6. Then 1/1.6= 6.25x10^18

Question 4

Charge is quantised?

Answer 4

It can only have certain values of multiples of 1.6, this is because half and quaterelectron can never be added, it has to be a multiple, only integer values!

Question 5

What are electrolyted

Answer 5

This is a liquid that can carry current , so like ions etc

Question 6

Current in metal atoms?

How

Answer 6

Metal atoms form ions of positive charge and delocalised electrons which make the strong metallic bonding

However if charge applied to ends then the electrons can move and carry a current

For example make one end of thr wire posit be and one end negative the you csn carry a current

Question 7

Current direction

Answer 7

Actually negative to posit be, but conventionally positive to negative big to small terminal

Question 8

How does current increase

Answer 8

Either more electrons passing through a point per second
(So like greater cross sectional area)
Or current ones move faster

Question 9

So how does an electrolyte Cary current

Answer 9

Electrolyte is a solution of positive and negative ions whichare charge carriers

If a cathode and anode negative and positive electrodes are placed, then a current is produced as the movement of charged ions go to the eleftrodes

Question 10

Measuring current using ammeters- what characteristic do they have

Answer 10

V=IR, I= V/R, ideally you want no resistance so that all the current can be read and no reffed ton current happens, as high resistances would decrease the amount of current available

Ideally zero resists for so noe ffect on current it measures and you actually get proper raw output

Question 11

Conservation fi charge

Answer 11

Charge cannot be created or destroyed, and total amount of charge is constant in the universe and in a closed envrjkme t

Question 12

Krichoffs First law

Answer 12

States that the current going into a junction is = to the sum of the current going out of a junction

This relates to the conservation of CHARGE, because charge is a product of current in time !

Can be written as Ein = Eout

Question 13

Even if current is leaked how does does still abide

Answer 13

Earth will give back current to the circular so charge is conserved , here at the
Leer station it’s all one big circuit, and current returned

Question 14

What is number density

So what does a higher number density mean

Answer 14

Essentially the number of FREE ELECTRONS per m3 of a material

Higher number density = more free electrons, so More ability to be a better conductor

Question 15

Classify materials in order of number density?

Answer 15

Metals have highest , conductors

Insulators have the lowest that’s why insulate
Semiconductor in between and this varies when different cinditons applied to them

Wax insulator

Semiconductor silicon and germanium

Conductor copper else zinc GRAPHENE etc

As a result to reach same current s sic duct or a semiconductor electrons have tomkove so much faster

Question 16

Electric current new equation

Answer 16

I= A x N x E x V

Where V is mean drift velocity

Where A is cross sectional area

Question 17

So how dies Velocity relate to cross sectional area

Answer 17

Ugh equation your see that velocity si inversely proportional to are

So decrease are increase velocity

But not necaseily increase current because a DECREASE INNAREA ALSO INCREASES RESISTANCE (we will see later)

And area of circle is 4pi r2

Question 18

Explain how electrons have a mean drift velocity in a wire (exam styled 3 marker)

Answer 18

• free electrons make collisions with the positive metal ions, giving them a RANDOM VELOCITY
• free electrons drift towards the positive terminal of the supply ACROSS THE LENGTH OF THE WIRE
• the distance travelled per unit time in the ln geht of the wire is the mean drift velocity

So
1) electrons free collide with positive ions to give a random velocity
2) these will difft towards the
Leitbegriffe end of thr supply across the length of the wire
3) the distance travelled per unit time is the mean drift velocity along the length of the wire