P5 Flashcards
state the main sources of electricity + the type of electricity they generate
Most electricity is generated with steam turbines using fossil fuels,
whats d.c electricity
d.c electricity = direct current ,an electric current flowing in one direction only.
whats a.c
alternating current
an electric current that reverses its direction many times a second at regular intervals
whats the frequency of mains electricity
The two commonly used frequencies are 50 Hz and 60 Hz
how many times does mains electricity change direction every second ?
the direction of the current and voltage changes 100 times per second.
whats the potential difference of mains electricity
The wire covered in brown plastic is the live wire. This carries the 230 V alternating potential difference from the power supply. The wire covered in blue plastic is the neutral wire and this completes the circuit from the appliance back to the supply.
oscilloscope
electronic test instrument that graphically displays varying signal voltages
label the plug
earth wire - striped goes to the top
neutral wire - fold over blue wire
live wire - brown , the one thats on the right
all are copper wires which are good conductors
label the rest of the plug
the thing that looks like the battery on the side = the fuse
the thinf at the bottom of all the wires is the cable grip
the wire/lead is called the outer insulation
case is plastic - plastics a good insulator
what links frequency and period
frequency = 1
———————
periodic time
periodic time = 1
————————
frequency
5 safety rules for mains electricity
no water near check for damages wires + cables unplug if not using dont block plug sockets turn it off at wall when plugging in
what material is the cable insulator made from and why
Synthetic rubber compounds are used widely for insulation and sheathing of cables for flexible and for heavy duty applications. Many variations are possible, with conductor temperature ratings from 60°C to 180°C, as well as resistance to oil, ozone and ultra-violet radiation depending on the formulation.
whats the role of an earth wire ?
Earthing is used to protect you from an electric shock.
what does the neutral wire do
returns the electricity to the generator after it has passed through
what does the live wire do
connected directly to the generator - carries current at very high voltage
what material is used for the 3 pins on a plug and why
Brass material is resistant to overheating. It is very important for pins used in electric plugs to resist heat as overheating may cause fire.
how does the fuse protect
The fuse breaks the circuit if a fault in an appliance causes too much current to flow. This protects the wiring and the appliance if something goes wrong.
how does a circuit breaker work
i ts basic function is to interrupt current flow after protective relays detect a fault.
2 advantages of a circuit breaker over a fuse
CB = quicker , more reliable
whats an rccb
Residual Current Circuit Breaker
purpose of an rccb
its an electrical wiring device that disconnects the circuit whenever there is leakage of current flow through the Human body or the current is not balanced between the phaseconductor.
definition of power and its unit
power is the amount of energy transferred or converted per unit time (watts)
power equation
power = potential difference × current
energy transferred
watts / 1000 = the kW
