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38 Cards in this Set
- Front
- Back
What is the definition of electric current?
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the movement of free electrons from one point in a conductor to another.
the movement is due to the influence of a difference of potential existing across the conductor. |
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What are the 3 fundamental elements of Electric Current?
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1. Voltage
2. Current 3. Resistance |
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What is another name for voltage?
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Electromotive force
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what is the definition of Voltage?
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the difference in potential energy existing between two points in a conductor due to an unbalance electron population at these points.
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What are the names of the unbalanced points of electron population that give rise to voltage?
what are the populations in magnitude? |
Negative and Positive poles.
Negative = electron excess - lots Positive = electron deficiency - none |
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What is the direction of voltage flow in a circuit?
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From negative pole (e- excess) to positive pole (e- deficiency).
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What is the unit of measurement for voltage?
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Volts
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What is the definition of current?
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movement of electrons in a conductor
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what is power?
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Current x Voltage
P = IV |
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What is a fuse?
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a heat dissipator - when the instrument current gets too high, it melts and prevents damage. Wattage rating shows how much heat it can take.
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what type of division do you use to divide current in a circuit?
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parallel
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How do you divide voltage?
How do you divide current? |
Voltage: resistors in series.
Current: resistors in parallel. |
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How many components are in an instrument? What are they?
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6 - SIX - 6
-Power supply -Modifier -Light detector -Display -Microprocessor |
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What are 4 types of Power modifiers?
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-Capacitors
-Transistors -Amplifiers -Transformers |
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what is a Capacitor?
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it stores electrical charge. When the switch is open, no charge; when closed, charge builds up across dielectric space.
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What is a Transistor?
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a semiconuctive device with an emittor and a collector, housed on a very thin semi-conductive material. Emits electrons as current.
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what is a transformer?
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a power supply modifier that increases or decreases the power intensity based on its size.
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what is a diode?
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a type of power modifier that convers AC to DC.
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What is the only way a diode will work?
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If the anode is Pos and
if the cathode is Neg. |
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What is a Rectifier?
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a diode that is used to convert AC to DC
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What are 5 types of light detectors?
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-Photovoltaic
-Phototube -Photomultiplier tube -Phototransistor -Photoconductive cell |
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What is a Photovoltaic?
-does it need power? |
a light detecting device.
no, needs no external power supply. |
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Why not use a photovoltaic?
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-wears out fast
-needs long periods of light -temperature causes inaccurate signals. |
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what is a phototube?
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like a photovoltaic cell
-needs a constant power supply -needs power modified to DC. -needs amplification. |
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What is a photomultiplier tube?
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a phototube with internal amplification.
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what is a phototransistor?
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a light detector like a phototube, only it has a lens that focuses light onto the electric sensitive material.
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what is a phototransistor used for?
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barcode readers.
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what is a Photocunductive cell?
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A very small light detector
-uses Cadmium sulfide -resistance decreases as it's exposed to light. |
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what is a photoconductive cell used for?
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In the flame photometer, it turns a light on when the flame is on so you don't have to peer down at it.
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what are 3 types of display systems?
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-Analog
-Digital -Cathode ray tube. |
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what are 2 types of analog display?
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-Direct (D'arsonval)
-Null balance (Wheatstone) |
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what are two types of Direct Analog displays?
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-Galvanometer
-Meter |
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what concept is d'arsonval movement based on?
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a sensing coil senses current from a permanent magnet;
Galvanometer: makes mirror flash Meter: makes coil w/ attached pointer align with mag field. |
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What is Wheatstone null balance detection based on?
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-2 fixed resistors, a POT, and an input transducor hooked up in parallel. By calibrating at zero, when a measurement is made it will cause the meter to deflect.
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What are 2 types of Digital display?
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-Electromechanical
-Electronic |
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what type of digital display is an oscillope
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electromechanical
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what emits light in electronic digital displays?
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glow tubes or Diodes.
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what is a microproccesor?
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semicundor that does math, logic, and makes decisions under stored control instructions.
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