P1- Electricity Flashcards
Closed switch
Completes circuit allowing current to flow
Open switch
Breaks a circuit preventing current from flowing
Celll
Source of electrical energy and potential difference
Battery
Multiple cells connected together
Diode
Only allows current to flow in one direction
Resistor
Resists flow of current in a circuit. It has a fixed value and is an ohmic conductor
Variable resistor
A component used to vary and control the current in a circuit
Lamp
A component that transfer electrical energy into light energy
Fuse
Safety device that can stop current flowing if the current flowing exceeds a certain value. It melts to stop
Thermistor
A component whose resistance is related to the temperature. As temp increases, resistance decreases
Ammeter
Measure current in a circuit connected in series
Voltmeter
Measure potential different between two points in a circuit connected in parallel
Light Dependant resistor
Resistance is related to amount of light falling on it. As light intensity increases, resistance decreases
Light Emitting Diode
Transforms electrical energy into light energy when current flows in one direction only
Current
The rate of flow of charge measured in Amps (A)
Voltage
The amount of energy per unit of charge measured in Volts (V)
Resistance
A measure of the opposition to current measures in Ohms
For electrical charge to flow through a closed circuit, what must the circuit have
A source of potential difference
Current formula symbol, unit and unit symbol
I, Amps, A
Voltage formula symbol, unit and unit symbol
V, Volts, V
Resistance formula symbol, unit and unit symbol
R, Ohms, ♎️
Charge formula symbol, unit and unit symbol
Q, Coulombs, C
Power formula symbol, unit and unit symbol
P, Watts, W
Charge flow equation
Current x Time Q=It
P.D equation
Current x Resitance V= IR
Total resistance equation
Resistance of component 1 + Resistance of component 2
Power equation
Current x Voltage P=IV
Power equation 2
Current squared x Resistance P=I^2R
Energy transferred equation
Power x Time E=Pt
Energy transferred equation 2
Charge flow x Voltage E= QV
Opposite charges…
Attract
Like charges…
Repel
What is all matter made up of
Tiny particles called atoms. Each atom consists of a positively charged nucleas with negatively charged electrons moving around it
4 things resistance is affected by
Length of the wire, thickness of the wire, material of the wire, temperature
How does resistance change based on the length of the wire
Increased length= Increased resistance
How does resistance change based on the thickness of the wire
Increased thickness= Decreased resistance
How does resistance change based on the material of the wire
More free electrons = Less resistance
How does resistance change based on the temperature
Increased temperature = Increased resistance
Internal energy equation
Kinetic energy of particles + Chemical potential energy
Ohms law
The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor. A component which obeys Ohms law is an Ohmic conductor
Ohmic resistors
As voltage increases, current increases, temp constant, resistance constant, gradient constant, follows Ohms law
IV Graphs
Fixed Resistor, Filament bulb, Diode
Fixed resistor
Directly proportional, Ohmic conductor
Filament bulb
Directly proportional in between but stops, Not an ohmic conductor
If you increase the supply voltage in a real lamp circuit, the resulting increase in current causes the filament bulb to do what
Increase in temperature, which increases resistance. This effectively limits the increase in current
Diode
Not directly proportional, Not an ohmic conductor
When connected in a forward direction, what resistance does the diode give
Low resistance
When connected in the reverse direction, what resistance does the diode give
High resistance
If a circuit with a lamp and a diode isn’t working, what has to be done
Flip the terminals of the cell or the diode as the diode only allows current to flow in one direction
Thermistor graph
Not a straight line (curve). Its resistance decreases as the temp increases. The current also increases. It can be used in thermostats and ovens (anything with temp control)
LDR graph
Not a straight line (curve). Resistance decreases when light intensity increases. Current also increases. Used in light sensing circuits, streets lights etc
Series circuit
One continuous, single loop with components connected one after another
What happens if a series circuit breaks
Whole circuit stops working
Current in series
Same everywhere in the circuit
Voltage in series
Shared across all of the components
Resistance in series
Total resistance is the sum of the individual resistances of each component
Parallel circuit
More than one loop (branches)
What happens if a component breaks in a parallel circuit
The other components on other branches will still work
Current in parallel
Shared/split between the branches
Voltage in parallel
All components gave the same voltage on each branch
Resistance in parallel
More components in parallel, lower total resistance (total resistance is less than the resistance of the smallest component)
What will components with a greater resistance have
A higher share of voltage
In a parallel circuit what will branches with the highest resistance also have
The lowest current
Alternating current
Current which changes direction repeatedly
Direct current
Current which flows in only one direction
Frequency of Mains electricity in UK
50Hz
Voltage of Mains electricity supplied to UK homes
230V
What is the colour of the live wire
Brown
What is the purpose of the live wire
To supply electrical energy (230V) with a fuse attached
What colour is the neutral wire
Blue
What is the purpose of the neutral wire
To complete the circuit and has 0V
What colour is the earth wire
Green and yellow striped
What is the purpose of the earth wire
To be a safety wire and provide a path of least resistance for current to get to the earth in case of an electrical fault
What is a short circuit
Where the electrical current flows through an unintended, shorter pathway instead of following a circuit (e.g through a device or person)
Energy transferred equation (depending on power)
Energy transferred=
Power x Time (E= Pt)
Energy transferred equation (potential difference)
Energy transferred = Charge flow x Potential difference (E=QV)
Charge of a proton
+1
Relative mass of a proton
1
Charge of a neutron
0
Relative mass of a neutron
1
Charge of an electron
-1
Relative mass of an electron
1/2000 (very little)
What are electrical fields
The electrical field is the space around an electrical charge where another charged particle would experience a force
What direction do the arrows face in an electrical field from an isolated positive charge
Outwards
What direction do the arrows face in an electrical field from an isolated negative charge
Inwards
What is a build up of static caused by
Friction
What happens to the potential difference between the object an earth when electric charge builds
Increases
What is the National Grid
A giant system of cables and transformers that cover the UK and connect power stations to consumers
What is needed to transmit the huge amount of power needed in the National Grid
Either a high potential difference or a high currenr
Role of the Step Up transformer
Increase PD and decrease current, to reduce energy losses as heat in the transmission cables
What is increased by the Step Up transformer
Potential difference
What is decreased by the Step Up transformer
Current
Role of the Step Down transformer
Increase current and decrease PD to make it safe for the consumers
What is increased by the Step Down transformer
Current
What is decreased by the Step Down transformer
Potential difference
