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A-level Physics > Chapter 9&10: EPR and Electrical circuits > Flashcards

Chapter 9&10: EPR and Electrical circuits Flashcards

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1
Q

what is current

A

rate of flow of charge

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2
Q

what is current measured in

A

Amps

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3
Q

what is e.m.f (definition)

A

energy transferred from chemical energy (or another when not a battery/cell) to electrical energy per unit charge

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4
Q

what is e.m.f in terms of work done

A

emf is the work done on the charge

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5
Q

what is potential difference (p.d) in terms of work done

A

pd is the work done by the charge

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6
Q

what is resistance

A

the difficulty of making current pass through a component

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7
Q

give the four main EPR equations PIVIR EQVIT

A 
P = I x V
Power = Current x Potential difference
V = I x R
Potential difference = Current x Resistance
E = Q x V
Energy = Charge x Potential difference
Q = I x t
Charge = Current x time
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8
Q

what is the resistivity equation

A 
p = (R x A) / L
resistivity = (Resistance x Cross sectiona area) / Length
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9
Q

what is the elementary charge definition and value

A

the charge of a single electron

1.6 x 10^-19

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10
Q

what is the electron gun equation

A

e x V = 0.5 x m x v^2

elementary charge x potential difference = 0.5 x mass of electron x velocity of electron squared

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11
Q

explain what the electron gun equation (eV = 0.5mv^2) means

A

the work done by the electrical field in the electron gun is equal to the Kinetic energy of the electron at the anode in the electron gun

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12
Q

what is Ohm’s Law

A

current and potential difference are directly proportional to each other given the materials temperature remains constant

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13
Q

what is resistance measured in

A

Ohms Ω

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14
Q

describe and explain the IV graph of a fixed ohmic resistor

A

straight line that passes through origin because resistance is constant so I and V are directly proportional

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15
Q

describe and explain the IV graph of a bulb

A

curved s shape line that passes through origin

Because as pd increases bulb gets hotter so resistance increases making gradient shallower

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16
Q

describe and explain the IV graph of a diode

A

flat line for I = 0 until a certain pd then increases rapidly
because diode only allows current to pass in one direction and requires a certain input pd to begin to function

17
Q

describe and explain the IV graph of a thermistor

A

straight line that passes through origin. Cold thermistor is shallower hot thermistor is steeper
Low resistance when hot but high resistance when cold

18
Q

describe and explain the IV graph of an LDR

A

straight line that passes through the origin. Shallow when dark but steep when light
because low resistance when light and high resistance when dark

19
Q

what is the electrical energy joules J equation

A

E = P x t

Electrical energy transferred (J) = Power of device (W) x time that is used for (s)

20
Q

what is the electrical energy kWh equation

A

E = P x t

Electrical energy transferred (kWh) = Power of device (kW) x time for which it is used for (h)

21
Q

what is internal resistance

A

resistance within a cell or battery

22
Q

what is terminal pd

A

pd across the whole circuit

23
Q

what is Kirchhoffs first law

A

total current entering a junction is equal to the total current leaving the junction

24
Q

what is Kirchhoffs second law

A

sum of the emf is equal to the sum of the pd around a closed loop

25
Q

what is a potential divider circuit

A

series circuit where two components are next to each other and share the current

26
Q

what are the two emf equations

A 
Ɛ = V + Ir 
Emf = pd + (current x internal resistance)
Ɛ = I(R + r)
Emf = current(resistance + internal resistance)
27
Q

what is charge measured in

A

Coulomb C

28
Q

how does an electron gun work

A

> heat the filament (cathode) to release the electrons from the metal into the vacuum
then record how fast electrons are travelling when they reach the anode

29
Q

why does the electron gun use a vacuum

A

so electrons dont collide with obstacles losing energy

30
Q

during the electron gun experiment what is the KE of the electrons at the cathode and anode

A

at the cathode KE = 0

at the anode KE = 0.5 x m x v^2

A-level Physics (24 decks)

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