P2.3 Electricity Flashcards
What is meant by the term electricity?
The flow of negatively charged electrons around a circuit
What do conductors have to make them work?
Free electrons
How do insulators work?
They do not have free electrons
How does current flow?
From the negative terminal to the positive terminal
What unit is charge in?
Couloms
What unit is current (i) in?
Amps
What unit is time in?
Seconds
What is the formula for total charge?
Charge= current x time
What is meant by voltage?
The force of the electrons flowing around the current which comes from the batteries and is used up in all components
When will voltage only be provided to a circuit?
If one side has a negative terminal and the other side has a positive terminal
What is meant by the total voltage in the circuit? (Def)
The sum of the batteries that are connected the right way minus the batteries that are connected the wrong way
What is an ammeter used to measure and how is it connected?
Used to measure current and is connected in series
What happens to the current when it is in series?
It is the same at all points
What happens to the current when it is in parallel?
Current is divided amongst all branches
What does a voltmeter measure and how is it connected?
Measures voltage
Connected in parallel
What is meant by resistance?
The opposition to the flow of a current through a wire or component
What is the formula for voltage?
Voltage=current x resistance
What unit is voltage gave in?
Volts
What unit is resistance gave in?
Ohms
What are the 4 factors that affect resistance?
Length
Cross sectional area
Material
Temperature
What does Ohms Law state?
At a constant temperature the current through a conductor is directly proportional to the voltage across it
In a graph showing the current in a filament bulb, why will the graph NOT be directly proportional to the voltage applied?
The temperature is increasing inside of the filament bulb
In a series circuit, what is the Rtotal?
Rtotal = R1+R2….
In a parallels circuit what is the Rtotal?
Rtotal= R1 x R2/ R1+R2
What causes Joule heating?
Electrons collide with atoms as they pass through a conductor, the light electrons loose energy whilst the heavy electrons gain energy which leads to an increase in vibration
What is the formula for energy transferred?
energy transferred = voltage × charge
or
energy transferred = voltage × current × time
What unit is energy in?
Joules
What is the formula for (electrical) power?
electrical power = voltage × current
What unit is power in?
Watts
What does Joules law state?
Joule’s law states that
the power generated in an
electrical component is the
product of the current in the
component and the voltage
across it
What is the formula for the number of units used?
number of units used = power rating (in kilowatts) × time (in hours)
What is the formula for the total cost?
total cost = number of units used × cost per unit
How does a one way switch work?
When the switch is open there is air between the conducting contacts and because air is an insulator, no current flows
What wire has blue insulation?
Neutral wire
What hand of the pin should the neutral wire be connected to?
The left hand of the pin
What wire has brown insulation?
The live wire
What hand of the pin should the neutral wire be connected to?
The right hand of the pin
What wire has striped yellow and green insulation?
The earth wire
What hand of the pin should the earth wire be connected to?
The top hand of the pin
What is the neutral wire?
The wire in the mains voltage system that is permanently 0 volts
What is the live wire?
The dangerous wire in the mains voltage system in which the voltage is changing
What is the earth wire?
The wire that connects the metal frame of the appliance to the earth
What is a fuse?
A short wire which melts to disconnect a circuit when too much current flows through it
What is the purpose of a fuse?
(e.g whom or what does it protect?)
To protect the appliance itself
What is the purpose of an earth wire?
To prevent harm falling onto the user
Define the term “double insulation”
A safety technique where the electrical appliance is encased in an insulating plastic to prevent the user coming into contact with a live wire and being harmed
What is cell polarity?
Cell polarity is concerned
with which end of a cell is
positive and which end is
negative
In a parallel circuit with 3 sets of resistors, what is the formula for Rtotal?
1/Rt= 1/R1 + 1/R2 + 1/R3…
