p2 - electricity Flashcards
(24 cards)
what is current
the flow of electrical charge
what is potential difference
voltage, how much electrical energy is transferred across a current
what is resistance
a measure of how difficult it is for current to flow
what is an ohmic resistor
a resistor with resistance that doesn’t change when current does, it is also directly proportional to p.d (if the temp stays constant)
what does the resistance of a diode depend on
direction of the current as they have a very high resistance in the reverse direction
what is a thermistor
a resistor that changes its resistance with temperature
where should voltmeters be connected
in parallel with measuring component
where should ammeters be connected
in series with measuring component
what is a circuit
a closed loop that an electrical current can flow through
how can p.d be calculated in an in-series circuit
adding up all the p.ds across each component
how to find resistance of an in-series circuit
adding up all the resistances of each resistor
what happens to current in a parallel circuit
shared across each branch
what is a dc power supply
direct potential difference, p.d always positive, flows only one direction
what is an ac power supply
an alternating potential difference, alternates between + and - p.d, mains electricity is ac
what is mains electricity
ac power supply, frequency of 50hz, p.d of 230v
what is the brown wire
live wire, contains alternating p.d
what is the blue wire
neutral wire, 0v p.d, completes circuit
what is the green and yellow wire
earth wire, safety, provides a paths to earth for current if there’s a fault to prevent electric shocks
what is the national grid
system of cables and transformers across the country that links power stations to consumers
what do transformers do and why
change the p.d and current of an electricity supply, as if they carried a high current for too long they would get hot which would waste energy
what do step-up transformers do
increase the p.d and decrease the current (step-down transformers do opposite)
how do insulating materials become charged
being rubbed together, due to friction causing electrons to jump from one material to another
what is a spark
when a conducting object is placed near a negatively charged object and electrons jump the gap, a spark appears
what is an electric field
a region where a charged object will experience a force
