Electric Circuits Flashcards
Define potential difference
potential difference is the energy transferred(or work done)between two points in a circuit per unit charge(V=W/Q)
Define emf
emf is the work done per unit charge by the power supply or cell, converting energy into electrical potential energy of the charges
Define current
the rate of flow of charge(I=∆Q/∆t)
Define power
the rate of transfer of energy(P=E/t)
Define resistance
the ratio of pd to current (R=VI)
State Kirchhoff’s potential difference law
The sum of the potential difference drops is equal to the sum of the emfs around a closed a closed loop within a circuit-this is due to conservation of energy
State Kirchhoff’s current law
The sum of the currents into a junction is equal to the sum of the currents out of the junction -this is due to conservation of charge
Define lost volts
the energy per unit charge transferred to the internal resistance of a cell(Ir)
Define resistivity
the resistance of a unit cube
Describe what resistivity depends on:
Resistivity is independent of dimensions of the wire - it is unique to an individual material only and depends on temperature
Describe how resistivity of a thermistor changes with temperature
Resistivity of a thermistor decreases with temperature(as number density of charge carriers, n increases)
Describe how the resistivity of a metal filament changes with temperature
Resistivity of a metal filament increases with temperature (as drift velocity, v decreases due to more frequent collisions between electrons and ions)
