Electricity Flashcards by Kathleen anderson

What is current

Rate of flow of charge

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Potential difference/voltage

The engery change per coulomb of charge

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Power definition

The electrical energy transferred per second

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Direct current

When current flows in only one direction at all times

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What is alternating current

What current changes direction

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What’s the peak current

The maximum current in am a.c supply

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What’s the peak voltage

The maximum voltage in an a.c supply

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Period

The time taken for one wave to pass a point

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Frequentcy

The number of waves per second

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Electromotive force

The number of joules available to 1 coulomb of charge passing through thr cell

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Internal resistance

The opposition to the flow of charges through a circuits power supply

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External resistance

The opposition to the flow of charges Externally to the source

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Two types of electrical signals

Ac
Dc

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In a dc circuit the current flows in

One direction

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An a AC circuit the current

Changes different directionsa

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Mains supply rms voltage

230

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Peak voltage

325v

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Frequency if mains supply

50hz

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What’s the EMF

Energy supplied to each colomb of charge in a battery

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What’s voltage

The engery supplied to each colomb of charge

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What is emf measured in

Volts

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A TPD of 4v

The voltage measured is 4v when cutrent is drawn from a cell

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Can charge be passed from the capacitor

No charge passes through

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Why can charge not be passed through a capitol

Because there is an insulator within the two metal plates

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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

In a conductors a43 thier bands ir not

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