Sensing

Question 1

Charge equation

Answer 1

Q=IT

Question 2

Kirchoffs 1st law

Answer 2

Conservation of charge
Currents into a point = current leaving a point

Question 3

Potential difference

Answer 3

Difference in electrical potential energy between two points (per unit of charge)

Question 4

Kirchoffs 2nd law

Answer 4

Conservation of energy
Potential difference of a complete loop is always 0

Question 5

Conduction under the microscope

Answer 5

• electrons move at 10^6 m/s, motion is random and doesn’t result in a current.
• when a potential difference is applied, the electrons feel a force pulling them towards the positive side. This produces a drift velocity.
• when a metal is cold positively charged ions do not move so electrons are less obstructed.
• when a metal is hot the ions move a lot more, so the electrons are scattered off of them more.
• alloys have a higher resistance as regular patterns have been disrupted.

Question 6

Drift velocity

Answer 6

Total displacement/ time

Question 7

Drift velocity equation things

Answer 7

Q= LAne
I= nAve
n- charge carriers per unit volume (m^-3)

Question 8

Insulators

Answer 8

Low conductivity
Start to conduct when softened or melted

Question 9

Semi conductors

Answer 9

1 atom in 10^12 is ionised at room temp, low conductivity
When heated more atoms become ionised, charge carrier density increases, increasing conductivity

Question 10

Sensitivity equation

Answer 10

Output PD/ input lux or temp

Question 11

A perfect voltmeter

Answer 11

Has infinite resistance
Draws no current

Question 12

Perfect ammeter

Answer 12

Has zero resistance
No voltage over ammeter

Question 13

Direct current

Answer 13

Flows from the positive terminal to the negative terminal

Question 14

Current

Answer 14

Rate of flow of charge
In series current is the at all points
In parallel current is spilt between branches

Question 15

Work done equation

Answer 15

Charge x voltage

Question 16

Joule heating

Answer 16

A resistance opposes the flow of charge, causing energy to be wasted as heat

Question 17

Conductance

Answer 17

A measure of how easily electrons can flow through a given material

Question 18

How semi conductors work

Answer 18

Number of mobile charge carriers increases with a factor, meaning there ability to conduct also increases

Question 19

EMF

Answer 19

Energy provided by the source per unit of charge

Question 20

Internal resistance

Answer 20

The resistance inside a power supply due to the materials it consists of