Yr 12 - Charge & Current - 1 Flashcards
(42 cards)
Electric Potential Energy
Energy required to move a charge against an electric field.
Potential Energy OR (Potential)
Potential energy per unit charge.
Potential = JC^-1
- So we don’t have to worry about how much charge there is.
Potential VS Electrical potential energy
- Potential depends on ‘Separation Distance’
- Electrical Potential Energy depends on ‘Separation Distance’ & ‘Charge Size’.
Charge
Physical property that causes matter to move.
- Coulomb’s
How to the 3 charges interact with each other?
Positive - Negative = Attract
Positive - Positive = Repel
Neutral = No interaction
Potential Difference
Difference in electric potential energy between 2 points.
- Due to charge doing work on circuit components.
Why are Thunderstorms so powerful?
✱ (-) charge builds any bottom of storm cloud
✱ Earths surface is made of (+) & (-) charge
✱ (-) cloud charge attracts (+) ground and repels (-) ground.
✱ Therefore, net (+) ground and net (-) cloud.
✱ Higher cloud = Greater separation distance. ∴ greater Ep
✱ Each (-) lightning charge looses up to 1,000,000J as its hits the ground (Potential Difference)
✱ Ep converted into Ke ∴ very hot
EMF
Electric Potential produced by a source of EMF (battery, power supply etc)
- EMF source does work on charges passing through
- Term used for components that increase Ep of charge.
Electric Current
Rate of flow of charged particles (Amps)
1 Amp
1 coulomb passing a point per second
Usual Direction of current flow
(+) to (-)
Conventional Current
Current flowing from (+) to (-).
Electron Flow
Flow of electrons from (-) to (+) as negatively charged.
- Opposite to conventional current
Equation for Charge
Q = I T
- Ignore (-) and just use modulus. (Check with Teacher)
Charge of an electron and Proton
e = -1.6 x 10 ^-19
p = 1.6 x 10 ^-19
Equation for number of electrons
No e = Total charge / e (electron charge).
Kirchhoff’s 1st Law
Sum of current into a node/junction = sum of current out.
- Due to conservation of charge
Conservation of charge
Charge cannot be created/destroyed. The sum of charge in any interaction must be the same before and after.
1 Coulomb
Charge flowing through a point per second where there is 1A current.
Formula for No electrons (No e)
NO e = ∑ Current / e
e = Charge of electron (-1.6x10^-19)
Conductor
Material with a high charge carrier density.
- Current free to flow
Semi-Conductor
Material with a medium charge carrier density.
- Partial current can flow
Insulator & Perfect Insulator
Material with a low charge carrier density
- Minimal current can flow (Insulator)
- No current can flow (Perfect Insulator)
Equation for number of charge carriers per / m^3
n = N / V
n = no. charge carriers / m^3
N = no. charge carriers in material
V = Volume of material
