P2 - Electricity Flashcards
What colour is the Earth wire?
Green and yellow
What do AC and DC mean?
AC - Alternating current. When constantly swapping directions, electrons bump into each other and pass the charge along (most common)
DC - DIrect current. Friction of electrons trying to get through creates energy.
What is a diode and what does it look like?
A diode only lets electricity pass one way (+ or -). Looks like a skip forwards button in a circle.
Which wire is blue?
The neutral wire
The live wire is blue. True or false?
False - the live wire is brown (just like revision)
The neutral wire is blue
What does potential difference mean? What is its units?
Voltz - V
Q is the symbol for Coulombs, which is the unit for resistance. True or false?
False - Q is the symbol for coulombs, but coulombs are the units for charge
When electricity flows through a resistor, what happens?
It becomes hot - the resistor is making it more difficult for electrons to pass through, so the friction creates thermal energy, which is heat
What are the two formulas for current?
Charge (coulombs) ÷ time (seconds)
OR
Voltz (V) ÷ Resistance (Ohms)
In a series circuit, the current is 10A at component 1
a) What is the current for component 2?
b) What is the voltage at component 3?
(series circuit - 12V, 10A, 3 components)
a) 10A
b) 4V
Complete these sentences about series circuits:
Potential difference is…
Current is the…
Resistance…
Shared (1stV + 2ndV ...= totalV) Same everywhere (1stI =2ndI ...) Adds up (1stR + 2ndR ...= totalR)
Complete the sentences about parallel circuits:
Potential difference is…
Current is the…
Same everywhere (1stV =2ndV ...) Shared (1stI + 2ndI ...= total I)
Why does increasing the amount of resistors in a parallel circuit decrease the resistance?
The total current through the circuit increases, so the total resistance decreases (downwards curve on a graph)
Mains supply is AC
Battery supply is DC
True or false?
True
Energy transferred =
Charge (Coulombs) x Voltage (V)
What does the national grid do?
It is a system of giant cables and transformers that covers the UK, connecting power stations to consumers of electricity.
What happens if one bulb of many stops working in a series circuit? What about in a parallel circuit?
All the bulbs in the circuit turn off as there is no longer a complete circuit through that bulb - as it is broken. However, electrons have a way of getting around a bulb in a parallel circuit, so the entire circuit doesn’t turn off as it is sill a complete circuit
Resitance is directly/ indirectly proportional to the ;length of the circuit (cm)
Directly proportional
The step up transformer increases/ decreases the voltage.
Which is true?
Increases the voltage
Step-down transformers decrease the voltage
What’s the formula for the voltage of the primary/ secondary coil’s voltage?
Primary Voltz Amount of turns on primary coil
———————— = —————————————————–
Secondary Voltz Number of turns on secondary coil
Rearrange the order of these components, and give their rough voltage:
a) National Grid
b) Houses
c) Step-up transformer
d) Power station
e) Factories
f) Step-down transformer
d) Power station - 20,000V (500 Mega Watts)
c) Step-up transformer - 20,000 to 400,000V
a) National Grid - 400,000V
f) Step-down transfrormer - 400,000V to 33,000V
e) More than houses
- Step-down transformers here too
b) Houses/ domestic - 230V
How can power be lost through the wires of pylons and stuff?
Through resistance
Resistance has a heating effect, which increases the current. True or false?
True for some reason
Give the definition of a fuse
A fuse is a safety device which breaks when unsafe.