practical electricity

Question 1

filament lamp

Answer 1

adv- give a cosy and relaxed atm

disadvantage- only a small percent of the electrical energy supplied is converted to light

Question 2

fluorescent lamp

Answer 2

adv- energy efficient

disadvantage- cost more than filament lamp, contains mercury so must be handled with care

Question 3

power

Answer 3

P=VI
P=I^2R
P=V^2/R
SI unit =W

Question 4

electrical energy

Answer 4

E=Pt

SI unit = J

Question 5

cost of electricity consumption

Answer 5

E=P(kW)t(hours)

Question 6

renewable energy

Answer 6

defined as energy from sources that can be replenished naturally
solar power, hydroelectric power, wind power

Question 7

non-renewable energy

Answer 7

defined as energy from natural resources that cannot be replenished at a sustainable rate
nuclear power, fossil fuel

Question 8

danger of electricity

Answer 8

damaged insulation -exposed conducting wires can cause electric shocks when touched
overheating of cables - overloading of sockets/ inappropriate use of wires (thins wires have higher resistance, generates more heat) can cause fires
damp condition - water provides a conducting path for current which can cause electric shocks, burns or even death

Question 9

household cables

Answer 9

live - brown, carries current from the mains supply to the appliance, usually 240v
neutral- blue, complete the circuit by providing a return path to the mains supply for the current, stays close to 0v
earth - green and yellow, conducts excess current on the metal casing to the ground, no voltage

Question 10

safety features (1-3)

Answer 10

circuit breakers - switch off the electrical supply in a circuit when there is a surge of large current flowing through them that may be caused by overloading or short circuit (connected to live wire)
fuse - prevent excessive flow of current, its short thin wire heats up and melts when the current flowing through it exceeds its rated value (live wire)
switches - break or complete an electrical circuit, connected to live wire so the high voltage supplied to the metal casing of an appliance can be disconnected to prevent electric shocks

Question 11

safety features (4-6)

Answer 11

earthing - connecting a wire from the metal casing of an appliance to the ground , provided a path of least resistance for the large current from the live wire to flow to the ground
double insulation- for appliance that do not have earth wire (two pin plugs)
three pin plugs - parts of three pin plug