Electricity, P2 Flashcards
How must an ammeter be placed in a circuit
In series
How must a voltmeter be placed in a circuit
In parallel
charge flow formula
Current ร time ๐ = ๐ผ ๐ก
potential difference formula
current ร resistance ๐ = ๐ผ ๐
total resistance formula =
resistance of component 1 +
resistance of component 2
๐
๐
= ๐
1 + ๐
2
The 2 different formulas for power is
power = current ร potential difference ๐ = ๐ผ ๐
power = (current)2 ร resistance ๐ = ๐ผ2๐
What are the 2 formulas for energy transferred
energy transferred = power ร time ๐ธ = ๐๐ก
energy transferred = charge flow ร potential difference ๐ธ = ๐๐
How does energy transfer round a circuit?
Electrons are supplied with energy by a cell/battery or mains electricity, which then move through the wires to transfer energy
Does charge/current always flow from negative(-) to positive(+) or positive(+) to negative(-)?
Positive to negative. + to -
What are coulombs?
A large group of electrons in a circuit
What do coulombs (C) measure?
Charge (Q)
What is potential difference (p.d) measured in?
Volts
What is p.d the measure of?
How much energy is transferred to/by each coulomb of electrons/charge
What is current (I)?
The flow of charge
How do we measure current?
Using an ammeter, in Amps (A)
What is OHMS law?
V = I x R
Potential difference = Current x Resistance
When using a fixed resistor, are V (p.d) and I (current) directly proportional or indirectly proportional?
Directly proportional
Is resistance in a filament lamp constant or not constant
NOT constant
When using a filament lamp, does a larger current in the circuit equal a higher or lower resistance across the filament lamp?
Higher
What does LED stand for?
Light Emitting Diode
Do diodes allow flow of current in multiple directions?
No, one direction only (Low resistance in forward direction, high resistance in reverse direction)
In series circuitsโฆ
-Total p.d is shared between all components
-Current is the same for all components
-Total resistance = sum of resistances
In parallel circuitsโฆ
-p.d for each branch = total p.d of cell/battery
-Current is split between branches
-Adding more resistors decreases resistance
What colour is the neutral wire?
Blue
What colour is the live wire?
Brown
What colour is the earth wire?
Green and yellow
Role of earth wire
It is a safety feature: acts as an escape route for current that would otherwise cause an electric shock if appliance is touched
What is the UK mains voltage?
230V
What is a direct potential difference (p.d.)
A potential difference that only acts in one direction
What are the 3 types of fuse?
3A fuse, 5A fuse, 13A fuse
Every plug has a fuse connected to the live wire. What is a fuse?
A thin metal wire in a tube that is designed to melt or โblowโ if there is a fault that causes a high currents
What is the role of the national grid?
To distribute electricity to where it is needed?
What 5 components are in the national grid? Order them in terms of when they receive the electricity (first to last)
Power stationโ>Step up transformerโ>National grid cablesโ>Step down transformerโ>Homes
Why does current from current from power stations go straight to houses?
They produce a high current, so lots would be lost as heat due to the resistance of the cables
Role of a step up transformer
Increases the voltage to 123KV, which decreases the current reducing the power lost to heat in the cable
Role of a step down transformer
Reduces voltage down to a safer and usable 230V for for homes and businesses
What is the frequency of the mains supply? (Hz)
50Hz
What is static electricity?
When electrons are transferred between to insulating materials, they will remain charged
What happens if an object gains electrons?
It becomes negatively charged
What happens if an object loses electrons?
It becomes positively charged
Opposite charges โฆ
Attract
Like charges โฆ
Repel
What happens when you touch a Van Der Graaf generator?
Every part of you becomes positively charged because it takes away electrons, thatโs why your hairs stand up - they are repelled from your head
What is an electric field?
A region around a charged object where other charges objects experience a force
What is an electric field?
A region around a charged object where other charges objects experience a force
