electricity and circuits Flashcards
equation for power in terms of forces
power = work done/ time
unit for power
watt / joule per second
conventional current
current that flows from positive to negative
insulator
holds the electrons tightly to atoms so the electric currents cannot flow
conductor
substances which allow electrons to pass through it
coulomb
unit of charge
rules for a series circuit
- the current stays the same
- has no loops or branches
voltmeter
measures the amount of energy per electron
potential difference = …
voltage
the bigger the voltage, the bigger the …
current
doubling the resistance … the current
halves
light dependant resistor
(LDR) the resistance decreases as light intensity increases
thermistor
resistance decreases as temperature increases
diode
- the resistance of the diode is very high then decreases suddenly at a threshold voltage
- diodes only let current flow in one direction and only once the voltage has reached a threshold
why can electrons flow more easily through a smaller resistance
there are less forceful collisions with the ions in the wire, possibly due to shorter, wider or different metals
uses of diodes
- stops currents from flowing in the wrong direction to prevent damages, e.g. remote batteries
- diodes can be used to convert alternating current from mains electricity to direct current in a phone charger
equation for energy in terms of electric circuits
energy = voltage x current x time
how to reduce resistance in a circuit
- use low resistance metals such as copper
- make the wire thicker
- cool the wire so ions vibrate less
calculation for power using resistance
P = I^2 x R
alternating circuit
electricity that is generated when an electromagnet is rotated inside the coil of a machine called an alternator
live wire
230v connected to generator at power station. can be fatal if touched
neutral wire
return path of the power station to complete the circuit. should be 0v
earth wire
connected to the ground with a metal spike for safety. should be 0 volts
fuse
- limits the current in the live wire for safety
- too much current would heat up the wire and may cause fires