Electricity Flashcards
Purpose of fuse
If too much current passes through it it melts which breaks the circuit
Prevents device from being damaged (from too much current flowing through it)
What does the fuse do if too much current is passing through it
Melts
(Breaks circuit to prevent device being damaged from too high current)
Which part of a plug has a voltage of 230V
Live wire
Potential difference of Earth and Neutral wire
0V
What colour is the Earth wire
Green and yellow
What colour is the neutral wire
Blue
(Think water is neutral in chemistry and the sea (water) is blue)
What colour is the live wire
Brown
Equation linking charge current and time
Charge = current x time (QIT)
What is current
Rate of flow of charge
(Flow of charge per second)
Equation linking potential difference, current and resistance
Potential difference = current x resistance
V=IR
What does it mean if a circuit component is ohmic
Current flowing through it directly proportional to potential difference across it
Relationship between current and potential difference of a resistor (meaning when resistance is constant)
Directly proportional
As current doubles, potential difference also doubles as V= IR
True or false, in a parallel circuit the current on all the paths adds up to the current in the battery
True
True or false in a parallel circuit the potential difference is the same as the battery at each path
True
What’s different between current in parallel and series circuit
Series- same everywhere
Parallel- current from each path adds up to total current of battery
What’s difference between potential difference in parallel and series circuit
Series- potential difference of battery split between all components
Parallel- all components (paths) have same potential difference as battery
Rule for resistance and potential difference in series circuit
Total resistance = resistance of all components added together
Total potential difference (battery) = potential difference across all components added together
Which type of current only flows in one direction
Direct current (DC)
What type of current is the mains electricity
Alternating
(Keeps changing direction)
Frequency of mains electricity
50Hz
Power is the…
Energy transferred per second
Role of plastic case on device
Insulates it to prevent you getting an electric shock
How do step up transformers improve efficiency
Higher potential difference means less current needed as power= current x potential difference
Low current means less power wasted from heating of cables as power lost = current squared x resistance
Why does potential difference need to be decreased by step down transformers before reaching homes
To make it safe to use
Why is copper commonly used in wires
Good conductor
Can bend easily
Which way does current flow
Positive to negative side of battery
(Opposite to electrons why flow from negative to positive)
When plotting a graph to show relationship between current and potential difference when resistance is constant, what goes on each axis
Y axis is current
X axis is potential difference
Relationship between current and potential difference when resistance in constant
Directly proportional.
If one doubles so does the other as V=IR (potential difference = current x resistance)
One thing assumed for current and potential difference being directly proportional when resistance is constant
Temperature is constant
(Increasing temperature increases resistance)
Relationship between current and resistance for filament lamp (light bulb)
At higher voltages resistant is higher so there is less current
(F shape)
At higher voltages for a filament lamp why is there an increase in resistance
More current flowing increases temperature and higher temperature increases resistance
Why does a filament lamp not follow ohms law
Current and potential difference through lamp aren’t directly proportional
At higher voltages there is less current (but more resistance as the component heats up)
How many directions does current flow through a diode in
Only 1 direction
True or false, current can only flow through a diode in 1 direction
True
Which component has a very high resistance in the reverse direction which is why current flows through it in only 1 direction
Diode
3 ways to increase resistance of wire
Make wire longer
Make wire thinner
Make wire hotter
In a … circuit the components are all in one continuous loop
Series circuit
Big downside of series circuits
If one component breaks/ gets damaged then whole circuit will stop working as electrons can’t pass through
Which circuit does Vtotal= V1 + V2 + V3 apply to and what does it mean
Series
Total voltage of power pack is shared across all components
(Potential difference if all components will add up to potential difference of battery)
In what curcuit is current the same everywhere
Series
Rule for resistance in series circuit
Total resistance = resistance of all components added together
True or false, according to ohms law, in a series circuit components with a higher resistance have a higher voltage
True
As current is the same everywhere (constant) and V = IR so a greater V needs a greater R
Why are parallel circuits more useful than series circuits
Have more than 1 loop
If a component breaks, the current can still flow to other components
Rule for potential difference in parallel circuit
Potential difference is the same everywhere
All components (paths) have same potential difference as battery
Rule for current in parallel circuit
Current Split between each path
Current of all paths added together= total current
Rule for resistance in parallel circuit
Adding resistors decreases total resistance
For which type of circuit does adding resistors decrease total resistance
Parallel
(Opposite for series where more resistors increases total resistance)
What is the national grid
Giant network of transformers and wires that distribute electricity from power stations to homes
Role of Earth wire
Stops appliance becoming live which could cause an electric shock
Redirects current to the ground if there’s a fault
Conventional current meaning
In circuits current flows from positive to negative end of battery
What does the Earth wire connect to
Case of device
Electric field meaning
Area around charged object where a force would be exerted onto other charged objects
What happens when 2 insulators are rubbed together
Friction occurs, electrons transfer from one to another giving them both an overall charge (positive if electrons lost or negative if electrons build up)
Why won’t static electricity work on conductors
Charge flows through so can’t build up
Why won’t static electricity work on conductors
Charge flows through so can’t build up
Static electricity meaning
Build up of charge on 2 insulators
Variables in measuring resistance of long wire RPA
Dependent = resistance of wire
Independent= length of wire
Control- temperature of wire (Turn off power pack between readings and use low potential difference), material of wire
Method for measuring resistance of long wire RPA
DV- resistance of wire
IV- length of wire
CV- wire material and temperature
1)Attach the resistance wire to a ruler in series to measure its length
2) Set up a circuit by using crocodile clips to attach the power pack and ammeter in series to the resistance wire in a single loop (first one crocodile clip should be at 10cm, the other at 0cm)
4)Then connect the voltmeter to the resistance wire in parallel.
5) turn on the power pack, immediately record potential difference and current then turn off.
6) Move the 10cm crocodile clip along to 20cm and repeat step 5
7) keep doing this up to 50cm
8) use potential difference and current to calculate resistance of wire at each length with equation resistance = potential difference/ current
9) plot results on graph (resistance on y axis, length on x axis)
2 values needed to calculate resistance of wire in RPA
Potential difference, current
As resistance = potential difference/ current
In measuring resistance of wire RPA why does the power pack need to immediately be turned off inbetween readings
Prevents wire heating and increasing resistance due to heat (keeps it a fair test)
True or false, a higher resolution is more accurate
True
What type of error is a zero error
Systematic (human)
Zero error meaning
When an instrument doesn’t read zero when the quantity to be measured is zero
For resistance RPA why must you use a low potential difference
Prevent wire getting too hot which could burn you
Why does an increase in temperature increase resistance
As wire gets hot ions in wire vibrate faster
More collisions with electrons
Electrons can’t flow as easily
What type of error could cause the ammeter/ voltmeter readings to be too high in resistance RPA
Zero error
Length of wire doesn’t start at 0
How to calculate energy for SHC RPA with voltmeter and ammeter
Power= current x potential difference
Power x time = energy transferred
Specific heat capacity variables
IV- temperature of block
DV- energy transferred
CV- mass of block, material of block
How to set up RPA for testing electrical components
In series place ammeter, component and power pack
Add voltmeter around component in parallel
