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38 Cards in this Set

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What is the definition of electric current?
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.
What are the 3 fundamental elements of Electric Current?
1. Voltage
2. Current
3. Resistance
What is another name for voltage?
Electromotive force
what is the definition of Voltage?
the difference in potential energy existing between two points in a conductor due to an unbalance electron population at these points.
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
What is the direction of voltage flow in a circuit?
From negative pole (e- excess) to positive pole (e- deficiency).
What is the unit of measurement for voltage?
Volts
What is the definition of current?
movement of electrons in a conductor
what is power?
Current x Voltage

P = IV
What is a fuse?
a heat dissipator - when the instrument current gets too high, it melts and prevents damage. Wattage rating shows how much heat it can take.
what type of division do you use to divide current in a circuit?
parallel
How do you divide voltage?

How do you divide current?
Voltage: resistors in series.

Current: resistors in parallel.
How many components are in an instrument? What are they?
6 - SIX - 6
-Power supply
-Modifier
-Light detector
-Display
-Microprocessor
What are 4 types of Power modifiers?
-Capacitors
-Transistors
-Amplifiers
-Transformers
what is a Capacitor?
it stores electrical charge. When the switch is open, no charge; when closed, charge builds up across dielectric space.
What is a Transistor?
a semiconuctive device with an emittor and a collector, housed on a very thin semi-conductive material. Emits electrons as current.
what is a transformer?
a power supply modifier that increases or decreases the power intensity based on its size.
what is a diode?
a type of power modifier that convers AC to DC.
What is the only way a diode will work?
If the anode is Pos and
if the cathode is Neg.
What is a Rectifier?
a diode that is used to convert AC to DC
What are 5 types of light detectors?
-Photovoltaic
-Phototube
-Photomultiplier tube
-Phototransistor
-Photoconductive cell
What is a Photovoltaic?
-does it need power?
a light detecting device.
no, needs no external power supply.
Why not use a photovoltaic?
-wears out fast
-needs long periods of light
-temperature causes inaccurate signals.
what is a phototube?
like a photovoltaic cell
-needs a constant power supply
-needs power modified to DC.
-needs amplification.
What is a photomultiplier tube?
a phototube with internal amplification.
what is a phototransistor?
a light detector like a phototube, only it has a lens that focuses light onto the electric sensitive material.
what is a phototransistor used for?
barcode readers.
what is a Photocunductive cell?
A very small light detector
-uses Cadmium sulfide
-resistance decreases as it's exposed to light.
what is a photoconductive cell used for?
In the flame photometer, it turns a light on when the flame is on so you don't have to peer down at it.
what are 3 types of display systems?
-Analog
-Digital
-Cathode ray tube.
what are 2 types of analog display?
-Direct (D'arsonval)
-Null balance (Wheatstone)
what are two types of Direct Analog displays?
-Galvanometer
-Meter
what concept is d'arsonval movement based on?
a sensing coil senses current from a permanent magnet;
Galvanometer: makes mirror flash
Meter: makes coil w/ attached pointer align with mag field.
What is Wheatstone null balance detection based on?
-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.
What are 2 types of Digital display?
-Electromechanical
-Electronic
what type of digital display is an oscillope
electromechanical
what emits light in electronic digital displays?
glow tubes or Diodes.
what is a microproccesor?
semicundor that does math, logic, and makes decisions under stored control instructions.