P5 Flashcards

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1
Q

state the main sources of electricity + the type of electricity they generate

A

Most electricity is generated with steam turbines using fossil fuels,

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2
Q

whats d.c electricity

A

d.c electricity = direct current ,an electric current flowing in one direction only.

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3
Q

whats a.c

A

alternating current

an electric current that reverses its direction many times a second at regular intervals

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4
Q

whats the frequency of mains electricity

A

The two commonly used frequencies are 50 Hz and 60 Hz

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5
Q

how many times does mains electricity change direction every second ?

A

the direction of the current and voltage changes 100 times per second.

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6
Q

whats the potential difference of mains electricity

A

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.

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7
Q

oscilloscope

A

electronic test instrument that graphically displays varying signal voltages

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8
Q

label the plug

A

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

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9
Q

label the rest of the plug

A

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

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10
Q

what links frequency and period

A

frequency = 1
———————
periodic time

periodic time = 1
————————
frequency

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11
Q

5 safety rules for mains electricity

A
no water near 
check for damages wires + cables
unplug if not using 
dont block plug sockets 
turn it off at wall when plugging in
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12
Q

what material is the cable insulator made from and why

A

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.

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13
Q

whats the role of an earth wire ?

A

Earthing is used to protect you from an electric shock.

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14
Q

what does the neutral wire do

A

returns the electricity to the generator after it has passed through

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15
Q

what does the live wire do

A

connected directly to the generator - carries current at very high voltage

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16
Q

what material is used for the 3 pins on a plug and why

A

Brass material is resistant to overheating. It is very important for pins used in electric plugs to resist heat as overheating may cause fire.

17
Q

how does the fuse protect

A

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.

18
Q

how does a circuit breaker work

A

i ts basic function is to interrupt current flow after protective relays detect a fault.

19
Q

2 advantages of a circuit breaker over a fuse

A

CB = quicker , more reliable

20
Q

whats an rccb

A

Residual Current Circuit Breaker

21
Q

purpose of an rccb

A

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.

22
Q

definition of power and its unit

A

power is the amount of energy transferred or converted per unit time (watts)

23
Q

power equation

A

power = potential difference × current

24
Q

energy transferred

A

watts / 1000 = the kW