P5 Flashcards
Give an example of an AC (alternating current). - AC potential difference causes current to periodically reverse its direction
Mains
A battery is a __ supply, meaning the potential difference causes current to only flow in one direction
DC (direct current)
Mains supply has a frequency of ___ but has a supply potential difference of __
50Hz
230V
describe the live wire
- brown
- carries alternating potential difference from the supply
- potential difference between the live wire and earth is 230V
- DANGEROUS: touching it and connecting it to the earth causes a person to be electrocuted, so they could die
describe the neutral wire
- blue
- completes the circuit
- potential difference of 0V
Describe the earth wire
- green and yellow stripes
- potential difference of 0V
- only carries current if there’s a fault
- safety feature
National grid-
a system of cables and transformers linking power stations to consumers
What do step up transformers do?
- increase potential difference in the transmission lines
What do step down transformers do?
decrease potential difference to a safer voltage for use in homes
a high potential difference means high/low current
low
What does a low current mean in terms of energy?
- less energy lost through heating wire, so it’s a more efficient way to transfer energy
what the equation linking power, current and resistance?
Power = current2 x resistance
P= I2R
what equation links current, power and potential difference?
Power = potential difference x current
P = VI
The amount of energy an appliance transfers is dependant on…
- how long the appliance is on for
- power of appliance
when a polythene rod is rubbed with a duster, how do electrons move?
- from duster to the rod
- duster: lost electrons = positive charge
- rod: gained electrons = negative charge
when a perspex rod is rubbed with a duster, how do electrons move?
- from rod to the duster
a charge will experience a non-contact force from another charged object. this force is called?
electrostatic force
a charged object creates an ___ around itself
electric field
the direction of the arrow indicates whether the charge is __ or __
positive, negative
The separation of the field lines show…
how strong the force is
The build up of charge on an insulator can lead to ___, for example…
sparking, lightening
how do balloons on walls work?
shows that charged objects exert forces on one another.
the negatively charged balloon is attracted to the positive ions of the wall, and repels the negative electrons
