Electricity Flashcards
What is current
Rate of flow of charge
Potential difference/voltage
The engery change per coulomb of charge
Power definition
The electrical energy transferred per second
Direct current
When current flows in only one direction at all times
What is alternating current
What current changes direction
What’s the peak current
The maximum current in am a.c supply
What’s the peak voltage
The maximum voltage in an a.c supply
Period
The time taken for one wave to pass a point
Frequentcy
The number of waves per second
Electromotive force
The number of joules available to 1 coulomb of charge passing through thr cell
Internal resistance
The opposition to the flow of charges through a circuits power supply
External resistance
The opposition to the flow of charges Externally to the source
Two types of electrical signals
Ac
Dc
In a dc circuit the current flows in
One direction
An a AC circuit the current
Changes different directionsa
Mains supply rms voltage
230
Peak voltage
325v
Frequency if mains supply
50hz
What’s the EMF
Energy supplied to each colomb of charge in a battery
What’s voltage
The engery supplied to each colomb of charge
What is emf measured in
Volts
A TPD of 4v
The voltage measured is 4v when cutrent is drawn from a cell
Can charge be passed from the capacitor
No charge passes through
Why can charge not be passed through a capitol
Because there is an insulator within the two metal plates
What happens to charge when it reaches the capacitor
It stores the charge
Graph for charging a capacitor time v current
Flopping line down
Graph for charging capacitor time vs voltage
Slopping up
Graph for discharging capacitor time vs current
Sloping up
Why is the graph negative for discharging
Because it going the opposite way
What’s the definition of capacitors
Charged stored per volt
What’s capacitors measured in
Faraed
F
The higher the capacity what happens to the time taken to charge
It increases
The top of the voltage vs tome charging gqph represents
The supply voltage
If you reduce the resistance what will happen to the time
It will decease
On the voltage graph for capacity is the resistance is less then
There will be a higher peak ending at the same place
What resistance do conductors have
A very low resistance
What resistance do semi conductors have
Pure semi conductors have a very high resistance
What resistance do insulators have
A very high resistance
What is it called when an impurity is added to a semi - conductors
Doping
What are the upper levels called
Conduction bands
Can electrons travel well in the conduction band or not
Yes they are free to move
What are the lower bands called
Valance bands
Can electrons move jn the valance bands
No
In a conductors a43 thier bands ir not
No
Wince thier js no bands in thr conductors what can the electrons do
Move freely
How filled is the conduction band in a conductors
Partially
How big of a gap does the insulator have
A large gap
How full is the valance band for an insulator
Full
In a semi conductor how large is the gap
Small
As the temperature increases what happens to the conductivity of the semi conductors
Thr conductivity will increase because more electrons have more energy
Which group in the periodic table are used for semi conductors
Group 4
What happens to conductivity when you add an impurity
It’s improves
What’s is n type
Where an element with an extra eletron is added
What is p type
Where an element with one less electron is added
Over all whats the charge on a p type and an n type
Neutral
Uses of p-n junctions
Diodes
Led
Photo diodes
Photovoltaic cells
For forward bias what is connected were
Positive js connected to the p-type and negative is connected to the n type
For reverse bias
Positive is connected to the n type and negative is connected to the p-type
When do leds conduct
When they are connected in forward bias
What is the depletion layer
It is were the small potential difference is produced stopping any further moment of holes or electrons across the junction
For electrons to go from the n-type conduction band to the p type conduction band what does jt need
Engery
What happens to the electric field in reverse bias
It increases making it more difficult for conduction
In a led explains what happens
Electrons are push from the n-type conduction ro the p-type condiction band. Hole are pushed from the p-type valance band to the n type valance band. When they meet in the depletion layer the elevtron falls into the whole and they produce light engery
What does it mean when one of the led doesn’t light up
Electrons didn’t gain enough energy to move into the conduction band of the p-type
Why do wires have a large diameter
To orevent over heating
