Chapter 9&10: EPR and Electrical circuits Flashcards
what is current
rate of flow of charge
what is current measured in
Amps
what is e.m.f (definition)
energy transferred from chemical energy (or another when not a battery/cell) to electrical energy per unit charge
what is e.m.f in terms of work done
emf is the work done on the charge
what is potential difference (p.d) in terms of work done
pd is the work done by the charge
what is resistance
the difficulty of making current pass through a component
give the four main EPR equations PIVIR EQVIT
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
what is the resistivity equation
p = (R x A) / L resistivity = (Resistance x Cross sectiona area) / Length
what is the elementary charge definition and value
the charge of a single electron
1.6 x 10^-19
what is the electron gun equation
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
explain what the electron gun equation (eV = 0.5mv^2) means
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
what is Ohm’s Law
current and potential difference are directly proportional to each other given the materials temperature remains constant
what is resistance measured in
Ohms Ω
describe and explain the IV graph of a fixed ohmic resistor
straight line that passes through origin because resistance is constant so I and V are directly proportional
describe and explain the IV graph of a bulb
curved s shape line that passes through origin
Because as pd increases bulb gets hotter so resistance increases making gradient shallower
describe and explain the IV graph of a diode
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
describe and explain the IV graph of a thermistor
straight line that passes through origin. Cold thermistor is shallower hot thermistor is steeper
Low resistance when hot but high resistance when cold
describe and explain the IV graph of an LDR
straight line that passes through the origin. Shallow when dark but steep when light
because low resistance when light and high resistance when dark
what is the electrical energy joules J equation
E = P x t
Electrical energy transferred (J) = Power of device (W) x time that is used for (s)
what is the electrical energy kWh equation
E = P x t
Electrical energy transferred (kWh) = Power of device (kW) x time for which it is used for (h)
what is internal resistance
resistance within a cell or battery
what is terminal pd
pd across the whole circuit
what is Kirchhoffs first law
total current entering a junction is equal to the total current leaving the junction
what is Kirchhoffs second law
sum of the emf is equal to the sum of the pd around a closed loop
what is a potential divider circuit
series circuit where two components are next to each other and share the current
what are the two emf equations
Ɛ = V + Ir Emf = pd + (current x internal resistance) Ɛ = I(R + r) Emf = current(resistance + internal resistance)
what is charge measured in
Coulomb C
how does an electron gun work
> 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
why does the electron gun use a vacuum
so electrons dont collide with obstacles losing energy
during the electron gun experiment what is the KE of the electrons at the cathode and anode
at the cathode KE = 0
at the anode KE = 0.5 x m x v^2
