physics p6 Flashcards
how can you measure reaction time?
catch a falling ruler:
- person holds ruler above your hand and drops it
- the length of the ruler below your hand when you catch it indicates your reaction time
what is thinking distance?
distance travelled during the time the car travels before hitting brake
what factors affect thinking distance?
drinking alcohol
using drugs
fatigue/ tiredness
what is braking distance?
distance travelled while force of the brake is applied to the car
what are the factors that affect the braking distance?
brakes, surface car is driving on, speed
what is stopping distance?
total distance the car travels from seeing problem to stationary:
thinking distance + braking distance
what is renewable energy?
they will not run out in millions of years
what is non renewable energy?
they will run out in the next millions of years
give renewable energy sources
biofuels
the sun
tides
wind
waves
hot rocks beneath ground
water high up
give non renewable energy sources
nuclear fuels (e.g uranium)
fossil fuels (e.g coal, oil, gas)
what were nuclear fuels formed in?
stars
why has the use of energy sources changed overtime?
- population increase
- use of devices that use fuels like cars
- electricity generation
how do fossil fuels link to climate change?
burning fossil fuels produces carbon dioxide which contributes to climate change
what is the national grid?
the power stations, underground and overland wires, transformers that supply electricity
what do transformers do?
change the voltage (p.d) to reduce the heating effect
what do step up transformers do?
increase the p.d to nearly 400,000V
what do step down transformers do?
decrease the p.d to 230V you need at home
what is the order of national grid?
power station
step up transformer
grid network (275,000v)
step down transformer
grid network (132,000v)
transformer substations
offices/ homes
how can you show how energy is transferred in the national grid?
sankey diagram:
useful energy is straight + wasted energy moves away
what is the voltage of mains electricity?
230V
why is the heating loss minimised in national grid?
voltage is increased causing current to decrease
less current means less energy is dissipated
what is a direct current?
current flows in one direction
cells and batteries supply d.c
what is alternating current?
constantly changes direction
- from mains as it is anything plugged into a socket
what are the wires apart of the three pin plug?
live wire
neutral wire
earth wire
what is the live wire and where is it?
Brown wire that carries alternating current (230v)
on right side
what is the neutral wire and where is it?
Blue wire that completes the circuit
on the left side
what is the earth wire and where is it?
green + yellow wire that is the safety wire that is connected to ‘earth’ (large pole)
- in middle of plug
what does the fuse do?
- breaks circuit if there is too much current flowing by melting easily
- it protects the wiring
what is double insulation?
appliances with outer metal cases to prevent people getting electric shock
