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Physics > Yr 12 - Charge & Current - 1 > Flashcards

Yr 12 - Charge & Current - 1 Flashcards

1
Q

Electric Potential Energy

A

Energy required to move a charge against an electric field.

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2
Q

Potential Energy OR (Potential)

A

Potential energy per unit charge.

Potential = JC^-1

  • So we don’t have to worry about how much charge there is.
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3
Q

Potential VS Electrical potential energy

A
  • Potential depends on ‘Separation Distance’
  • Electrical Potential Energy depends on ‘Separation Distance’ & ‘Charge Size’.
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4
Q

Charge

A

Physical property that causes matter to move.

  • Coulomb’s
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5
Q

How to the 3 charges interact with each other?

A

Positive - Negative = Attract
Positive - Positive = Repel
Neutral = No interaction

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6
Q

Potential Difference

A

Difference in electric potential energy between 2 points.

  • Due to charge doing work on circuit components.
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7
Q

Why are Thunderstorms so powerful?

A

✱ (-) 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

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8
Q

EMF

A

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.
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9
Q

Electric Current

A

Rate of flow of charged particles (Amps)

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10
Q

1 Amp

A

1 coulomb passing a point per second

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11
Q

Usual Direction of current flow

A

(+) to (-)

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12
Q

Conventional Current

A

Current flowing from (+) to (-).

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13
Q

Electron Flow

A

Flow of electrons from (-) to (+) as negatively charged.

  • Opposite to conventional current
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14
Q

Equation for Charge

A

Q = I T

  • Ignore (-) and just use modulus. (Check with Teacher)
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15
Q

Charge of an electron and Proton

A

e = -1.6 x 10 ^-19
p = 1.6 x 10 ^-19

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16
Q

Equation for number of electrons

A

No e = Total charge / e (electron charge).

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17
Q

Kirchhoff’s 1st Law

A

Sum of current into a node/junction = sum of current out.
- Due to conservation of charge

18
Q

Conservation of charge

A

Charge cannot be created/destroyed. The sum of charge in any interaction must be the same before and after.

19
Q

1 Coulomb

A

Charge flowing through a point per second where there is 1A current.

20
Q

Formula for No electrons (No e)

A

NO e = ∑ Current / e

e = Charge of electron (-1.6x10^-19)

21
Q

Conductor

A

Material with a high charge carrier density.

  • Current free to flow
22
Q

Semi-Conductor

A

Material with a medium charge carrier density.

  • Partial current can flow
23
Q

Insulator & Perfect Insulator

A

Material with a low charge carrier density

  • Minimal current can flow (Insulator)
  • No current can flow (Perfect Insulator)
24
Q

Equation for number of charge carriers per / m^3

A

n = N / V

n = no. charge carriers / m^3
N = no. charge carriers in material
V = Volume of material

25
Q

What happens when you heat a thermistor

A

More electrons become free to move and therefore more current can flow.

26
Q

What happens if light intensity increases with an LDR?

A

More electrons are freed and therefore, the conductivity increases.

27
Q

What happens as energy flows into a material.

A

More electrons become freed and conductivity increases.

28
Q

What’s the equation for current?

A

I = Anev

I = Current (A)
A = Cross-sectional area (m^2)
n = Number of charge carriers / m^3
e = Electron charge (1.6x10^-19)
v = Drift Velocity - (ms^-1)

29
Q

Describe the motion of electrons

A

Random motion with an overall drift velocity.

30
Q

What are charge carriers?

A

Particles that can carry electrical charge.

31
Q

What is drift velocity

A

Average velocity of charge carriers.

32
Q

What is number density?

A

no. electrons per m^3

33
Q

What happens to energy when a charged particle is accelerated?

A

When a PD accelerates a charged particle the energy transferred is equal to the kinetic energy gained by the particle.

34
Q

1 Volt

A

PD between 2 points when a 1C charge passing between the points experiences a change in electric potential energy of 1J

35
Q

Circuit symbols for these components:

  • Cell
  • Battery
  • Resistor
  • Variable resistor
A

Cell: 2 vertical lines, longer one for positive terminal and shorter for negative terminal.

Battery: Same as cell but more horizontal lines in-between

Resistor: Empty rectangle

Variable resistor: Rectangle with NE arrow through

36
Q

Circuit symbols for these components:

  • LDR
  • Thermistor
  • Diode
  • Ammeter
    Voltmeter
A

LDR: Circle with resistor symbol inside, 2 arrows on top right pointing SW

Thermistor: Rectangle with tick through it

Diode: Play button

Ammeter: A

Voltmeter: V

37
Q

Circuit symbols for these components:

  • Fuse
  • Capacitor
  • Switch
A

Fuse: Rectangle with horizontal line through

Capacitor: Same as cell but both lines the same length

Switch: U already know it

38
Q

What does a Voltmeter do + info

A

Measures change in Ep across COMPONENT

  • Must be In parallel
  • Very high resistance so no current flows through
39
Q

Ammeter

A

Measures current through a position

  • Must be in series
40
Q

Equation for:
- Work
- EMF
- △ Ep

A

Work: W = QV

EMF: ε = W/Q

△ Ep: △Ep = 1/2mv^2

41
Q

Circuit symbols for this components:

  • LED (Light emitting diode)
A
  • Play button with 2 arrows on top left pointing NE
42
Q

IV graphs for these components:

  • Resistor
  • Filament bulb
  • Diode
A

Resistor - y=x

Filament bulb - f shape

Diode - Flat when -x but exponential increase when +x

Physics (18 decks)

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