Transcript Presentation1

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Power Diode
Resistors
LEDs
9V Battery
Electrolytic
Capacitors
NPN Transistors
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Batteries contain
chemicals which react with
one another to create a
pushing force also know
as voltage. Batteries have
to be connected the right
way to work, components
like this are said to be
polarised.
Symbol for a 9v battery
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A power diode is like a 1 way valve, it
prevents current from flowing back the
way it came and damaging circuit
components. It has 2 leads, an anode and
a cathode. The anode is made from a
material called P type. The cathode is
made from an N type material. The P type
material has 7 electrons so it will want to
gain an electron, because its missing an
electron its said to have a hole. The N
type material has 9 electrons so it will lose
an electron easily as it has 1 extra flowing
electron. Like the battery this component
is also polarised and has to be placed into
the circuit correctly.
Diode Symbol
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LED symbol
Like the diode this has an anode
and a cathode terminal and only
conducts electricity in one
direction. Also like the diode the
negative electrons flow one way
and the positive holes flow the
other way. An LED produces light
because the holes are at a much
lower energy level than the flowing
electrons. The electrons have to
lose energy to fill these holes and it
does this by giving off energy as
light (Photons).
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A resistor resists the flow of charge, hence the name resistor.
Resistors have colour bands around them to show how much flow
of charge they resist.
Resistor symbol
How a carbon film
resistor works
and how the
resistance can be
varied
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Interior of an electrolytic
capacitor
Electrolytic
capacitor
symbol
Capacitors store electric charge
within them. Electrolytic
capacitors are a different form of
capacitor with an electrolyte
within it which helps hold more
charge. A capacitor works similar
to how a lighting storm works.
The cloud would be one terminal
and the ground would be the
other. Once there is enough
charge at one terminal (the cloud)
it releases it as lighting to the
other terminal (the ground).
Electrolytic capacitors have a
positive and a negative end this
means that they are polarised.
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An NPN Transistor is similar to diode is built as the NPN means its N
type material, P type material and then N type material.
A transistor is like a switch, it has 3 leads on it: The collector, the
base and the emitter. A transistor is classified as off, if no current is
flowing through the base. This is because the base is what allows
current to flow from the collector to the emitter.
Transistor can also be used as an amplifier because when the base
has a current flowing through it, it also allows the collector to have
current flow through it and both of these currents flow out the
emitter. So you can add the charge from the base with collector and
this will what is being emitted.
NPN
Transistor
symbol
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When the circuit is complete and on, the capacitors will begin to
charge. They charge at different rates because no component is
made the same. Charging one capacitor will cause the current to
flow through the base of the transistor opposite that capacitor.
When the capacitor discharges through the base of its opposite
transistor, that transistor turns on. When that transistor is on it
prevents the capacitor attached to its collector from charging.
When the other capacitor is fully charged the transistor turns off and
allows the other capacitor to discharge through the resistor.
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The cycle repeats its self
many times per second.
Every time a transistor
turns on in this circuit the
LED between it and the
positive power supply
turns on.
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Some of the uses for a circuit like this are;
railroad crossings, emergency vehicle lights
and Christmas lights.
The time the LEDs stay lit for can be changed
by using different resistors or capacitors.
Resistor change how long it takes for the
charge to reach the components of the circuit
and the capacitors change how much charge
is needed before it will be discharged.

http://www.ami.ac.uk/courses/topics/0136_ec/ Date accessed 10/9/13

http://www.resistorguide.com/carbon-film-resistor/ Date accessed 12/9/13 By Resistor Guide
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http://www.capacitorguide.com/electrolytic-capacitor/ Date accessed By 12/9/13 By Capacitor Guide

http://www.resistorguide.com/fixed-resistor/ Date accessed 12/9/13 By Resistor Guide

http://www.resistorguide.com/what-is-a-resistor/ Date accessed 12/9/13 By Resistor Guide

http://www.resistorguide.com/resistance-of-a-resistor/ Date accessed 12/9/13 Resistor Guide

http://electronics.howstuffworks.com/led1.htm Date accessed 9/9/13 by HowStuffWorks
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http://electronics.howstuffworks.com/capacitor.htm Date accessed 9/9/13by HowStuffWorks

http://electronics.howstuffworks.com/capacitor1.htm Date accessed 9/9/13 by HowStuffWorks
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http://electronics.howstuffworks.com/transistor.htm Date accessed 9/9/13 by HowStuffWorks

http://www.instructables.com/id/How-Electronic-Switches-Work-For-Noobs-Relays-and/step5/Howa-Does-a-Transistor-Work/ Date accessed 10/9/13 By Instructables

http://electronics.howstuffworks.com/led2.htm Date accessed 10/9/13 By HowStuffWorks
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FUNWAY into Electronics volume 1 By Dick Smiths Electronics, Published 1994
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Physics Teacher
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Edmodo 5/9/13