P4 + P5 Flashcards
What is the job of an open switch?
Breaks the circuit to stop the electrical current.
What is the job of a closed switch
Allows the electrical current
What is the job of a cell?
A singular source of energy
What is the job of a battery?
multiple sources of energy
What is the job of a resistor?
Reduces electrical current
What is the job of a bulb?
Emits light
What is electricity?
the movement of electrons
What are the 2 types of electrical circuits?
Series and parallel
What is a series circuit?
it is connected with one pathway only (except a voltmeter)
What is a parallel circuit?
Connected with 2 or more pathways.
When drawing a circuit diagram, what way does the current flow?
From the positive side of the battery to the negative side.
What is the definition of current?
it is the rate of flow of charge
What is the equation for charge?
Q (charge) = I (current) x t (time)
What are the units for charge?
C or coulombs
What are the units for current?
Amps or A
What are the units for time?
secons or s
In a series circuit, the current is…
constant in all positions
In a parallel circuit, current can …
change in different positions
What is potential difference?
the difference in the amount of potential energy between 2 points.
What is potential difference measured in?
Volts
Why do electrons move?
because of electrostatic attration
What is the equation for energy?
E=QxV
What is the equation for resistance?
R (resistance) = I (current) / V (potential difference)
What is resistance measured in?
Ohms or that weird symbol
mA —> A ?
Divide by 1000
mA <— A
X 1000
How does static electricity work?
- An object becomes charged by adding or removing electrons.
- A potential difference occurs between the 2 objects.
- The potential difference causes current to flow between the surface until there’s no longer a potential difference.
What are the dangers of static electricity?
The sparks are enough to set a flammable material alight and cause a fire.
What is alternating current (AC)?
If the current constantly changes direction. Light flickering quickly
Mains electricity is an __ supply, with the UK mains supply being about ___v and having a frequency of __ Hz.
AC
230v
50Hz
What’s the graph for AC?
A wavy line
What’s the graph for DC?
A straight line across
What is direct current (DC)?
If the current flows in only one direction.
What has a DC supply?
Batteries and cells
How much does a typical battery supply of DC?
1.5v
What is the function of live wire?
Carries current around the circuit. Current goes into device.
What is the function of the neutral wire?
Carries current round the circuit away from device.
What is the function of the neutral wire?
Safety wire. Used to earth appliance when something goes wrong.
What is the colour for the live wire?
Brown
What’s the colour for the neutral wire?
Blue
What’s the colour for the earth wire?
Green/yellow
What do fuses prevent?
Fires
What does earth wires protect?
Electrocution
What are the 3 safety features appliances have?
The fuse, earth wire, switch
How and why does the fuse melt?
If a large current will flow through the fuse causing it to melt. This breaks the circuit and protect the appliance and user from harm.
What is the calculation for fuse?
Power = current x potential difference
What are the 8 energy stores?
Chemical
Thermal
Elastic
Magnetic
Gravitational potential
Electrostatic
Kinetic
Nuclear
What is the equation for efficiency?
Useful energy / total energy (x 100 if asking for percentage)
How do you increase efficiency?
To increase efficiency of a machine, the wasted energy transfers need TK be reduced with no change to the useful transfers.
