3: Electric Circuits Flashcards
Define current
The rate of flow of charged particles.
Define charge
A fundamental property of matter that governs how the particles are affected by an electric or magnetic field.
Explain the difference between conventional current and the flow of electrons.
Conventional current flows from positive to negative,
Electrons flow from negative to positive.
What is Ohm’s law?
Current is proportional to voltage at a constant temperature.
IV graph of an Ohmic conductor
IV graph of a filament bulb
IV graph of a thermistor
IV graph of a diode
What does each symbol represent in the resistivity equation?
R - resistance
ρ - resistivity
l - length
A - cross-sectional area
What does each symbol represent in the equation I = nqvA
I - current
n - charge carrier density (electrons per m3)
q - charge of an electron
v - average drift velocity
A - cross-sectional area
Potential divider equation
Define emf
Electromotive force
The total energy (chemical/mechanical) of a source (battery/generator) transferred to electrical energy when a unit charge passes through it.
Define potential difference
The energy transfer per coulomb of charge that flows from one point to the other.
Explain the change in resistance as temperature increases in a metallic conductor.
As temperature increases, metal ions vibrate more and the delocalised electrons collide more with the ions so resistance increases.
Explain the change in resistance as temperature increases in a thermistor.
As temperature increases, electrons have more energy so it is easier to transfer to the conduction band, so resistance decreases.
