Electricity Flashcards
define current and give a matching equation
The rate of flow of charge I = Q/t
Define voltage and give a matching equation
work done per unit charge V=W/Q
Define Electromotive force and provide a matching equation
work done by a voltage source per unit charge
emf = E/Q
give two equations for energy in terms of V
E= VQ
E=VIt
Give three equations for power
P = VI = I²R= V²/R
Give an equation for resistivity
ρ= RA/L
describe an equation to find resistivity
- measure the diameter of the wire, and find the cross sectional area
- set up s circuit with a voltmeter in parallel to the wire and an ammeter in series. have a ruler on the wire and crocodile clips determining its length
- measure V and I for different values of L
- use R=V/I to find resistance
- plot R against L and the gradient will be ρ/A
state ohm’s law.
in an ohmic conductor current is directly proportional to voltage at a constant temperature
describe superconductors
a superconductor has 0 resistance below their critical temperature.
they can be used in strong magnets and power transmission
In an LDR, describe the trend between light intensity and resistance
resistance decreases as light intensity increases
describe an I-V graph for an ohmic conductor
a straight line graph, that intersects the origin
describe an I-V graph for a diode
an exponential graph upwards in the positive quarter that goes through the origin
state Kirchhoff’s laws
total current into a junction = total current out
total emf around a loop = total potential difference dropped across the components
describe voltage across components of a parallel circuits
the voltage dropped across components in parallel is the same
describe a potential divider.
a group of resistors in series across a voltage source, that splits voltage between resistors in direct proportion to their resistance
