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Subelement T6
Electrical components, semiconductors, circuit diagrams, component functions
Section T6B
Semiconductors; basic principles of diodes and transistors
What class of electronic components is capable of using a voltage or current signal to control current flow?
  • Capacitors
  • Inductors
  • Resistors
  • Correct Answer
    Transistors

A transistor is an electronic switch that enables the current flow between two terminals if a voltage/current is present on a third.

Think of it as a push button switch. Push the button (apply current on the third pin) and current can flow between the other two. (very simplified)


For comparison:

A Capacitor stores electricity in the form of an electric field.

A resistor impedes the flow of electricity

An Inductor stores electricity in the form of a magnetic field.

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Tags: transistors electronics electrical current electrical components

What electronic component allows current to flow in only one direction?
  • Resistor
  • Fuse
  • Correct Answer
    Diode
  • Driven Element

A Diode is an electronic component that only allows current to flow one direction across it; the most commonly known type of diode these days is an LED (Light Emitting Diode). There are many flashlights and even house lights that are made of LEDs and they are indeed diodes which only allow current to flow in one direction (and then also happen to emit light when that happens).

A resistor allows current to flow both directions but resists the flow of current. A Fuse is something that generally allows current to flow in either direction but when too much current (or at too high of a voltage) flows across it the fuse "blows" (is destroyed) and the flow of current stops. A driven element is the part of an antenna that a transmitter causes to emit RF energy.

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Tags: electronics electrical components

Which of these components can be used as an electronic switch or amplifier?
  • Oscillator
  • Potentiometer
  • Correct Answer
    Transistor
  • Voltmeter

A transistor has three terminals; on the most common type of transistor (a bipolar transistor) these are Base, Collector, and Emitter. Current applied to the Base controls current flow between the collector and emitter, which allows it to work as an electronic switch. The amplifier capabilities are a little more complicated and have to do with the fact that the amount of current directed into the Base is directly proportional to the amount of current that can flow through the Collector and Emitter.

Conversely, a Varistor, also known as a voltage-dependent resistor, is a surge-protecting resistor that varies its resistance based on the applied voltage. A Potentiometer is a variable resistor, and a Thermister is a resistor whose resistance is dependent on temperature. None of these can be used as an electronic switch in any meaningful way.

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Tags: transistors electronics electrical components

Which of these components is made of three layers of semiconductor material?
  • Alternator
  • Correct Answer
    Bipolar junction transistor
  • Triode
  • Pentagrid converter

While the specifics of how a bipolar junction transistor works is beyond the scope of this explanation, it may be helpful to remember that nearly any time you hear the term "semiconductor" in casual electronic jargon someone is talking about either a transistor specifically or about something made with many transistors (such as an integrated circuit).

This can be remembered by two types of transistor “NPN” or “PNP” where each letter refers to one of the three layers that make them up.

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Tags: transistors electronics electrical components

Which of the following electronic components can amplify signals?
  • Correct Answer
    Transistor
  • Variable resistor
  • Electrolytic capacitor
  • Multi-cell battery

http://en.wikipedia.org/wiki/Transistor

A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal.

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Tags: transistors electronics electrical components

How is a semiconductor diode's cathode lead usually identified?
  • With the word "cathode"
  • Correct Answer
    With a stripe
  • With the letter "C"
  • All of these choices are correct

Electrical components can be small. Sometimes too small to be able to read letters or words. Might also think of a "striped cat"

Click for a list of schematic symbols.

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Tags: electronics electrical components

What does the abbreviation "LED" stand for?
  • Low Emission Diode
  • Correct Answer
    Light Emitting Diode
  • Liquid Emission Detector
  • Long Echo Delay

(L)ight

(E)mitting

(D)iode

http://en.wikipedia.org/wiki/Led

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Tags: electrical components electronics

What does the abbreviation "FET" stand for?
  • Correct Answer
    Field Effect Transistor
  • Fast Electron Transistor
  • Free Electron Transition
  • Field Emission Thickness

A Field Effect Transistor controls voltage and current like a regular transistor, but can operate on a much smaller signal, which makes it ideal for radio receivers. It operates using an electric field to control the shape of the channel in the semi-conductor material.

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Tags: electrical components electronics

What are the names of the two electrodes of a diode?
  • Plus and minus
  • Source and drain
  • Correct Answer
    Anode and cathode
  • Gate and base

Electrodes are refered to as either Anodes or Cathodes regardless of whether they are on a diode or other component. Current flows into an Anode and out of a Cathode.

Plus and Minus indicate a positive or negative voltage on a power source but are not strictly speaking names for electrodes. Source, Gate and Drain are terminals on a Field Effect Transistor (FET). Base, Collector and Emitter are terminals on a bipolar transistor.

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Tags: electrical components electronics

Which semiconductor component has an emitter electrode?
  • Correct Answer
    Bipolar transistor
  • Field effect transistor
  • Silicon diode
  • Bridge rectifier

The Bipolar transistor, of varieties NPN and PNP, is the most common kind of transistor -- indeed, when someone thinks of a transistor this is usually what they're referring to. There are three terminals, the Base, the Emitter, and the Collector.

Field Effect Transistors work differently from Bipolor transistors and instead have terminals Source, Drain, and Gate.

http://en.wikipedia.org/wiki/Field-effect_transistor

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Tags: electronics electrical components transistors

Which semiconductor component has a gate electrode?
  • Bipolar transistor
  • Correct Answer
    Field effect transistor
  • Silicon diode
  • Bridge rectifier

This one is a tricky one; many think that it's a bipolar transistor, but it's a FET, short for Field Effect Transistor. A bipolar transistor has a Base, Emitter, and Collector; a Field Effect Transistor has a Source, Drain, and Gate.

So remember; the field has a gate.

http://en.wikipedia.org/wiki/Field-effect_transistor[1]

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Tags: electrical components electronics transistors

What is the term that describes a transistor's ability to amplify a signal?
  • Correct Answer
    Gain
  • Forward resistance
  • Forward voltage drop
  • On resistance

Gain is defined as being the ratio of the output power to the input power, or in other words it refers to how much power is gained when passing through the transistor. Just remember that "you gain a lot through amplification".

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Tags: electronics transistors

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