Santa
Name the device that has 3 terminals and is used for switching and amplifying.
Transistor
The output section of a PLC controls the power applied to motors, relays, valves, etc, based on the logic that is programmed in the PLC program.
T/F
True, the logic is examined and calculated in the program, then the outputs are set based on these calculations.
What do the initials BPJT stand for?
Bi-Polar Junction Transistor. This transistor has 2 junctions, a PN and a NP junction.
A PNP (or NPN) transistor consists of three different "doped" materials and 3 junctions.
T/F
False, there are 2 junctions in the transistor, not 3,
hence the name "Bi-Polar"
A digital signal can have multiple values, 2v, 5v, 15v, etc
T/F
False, a digital signal only has 2 values, either ON or OFF (1 or 0)
Can you determine whether a transistor is an NPN or a PNP by physical examination?
No, to determine the type of transistor you must look up the data sheet provided by the manufacturer.
Which of the following determine the color emitted by a LED?
1-bias voltage 2-color of the lens 3- wavelength produced by the junction
The wavelength produced by the junction determines the color of the LED
A relay (or control relay) is a device for switching an external circuit.
T/F
True, a relay a simply an electrically operated switch.
Name the three parts of a bipolar junction transistor
Base, Collector and Emitter
How does a solid state relay differ from a control relay?
A solid state relay (SSR) has no moving parts as opposed to a conventional control relay.
What happens to the magnetic field inside a 3 phase motor when 3 phase power is applied?
The magnetic field will rotate, causing the rotor to rotate
How is the gain of an amplifier calculated?
The output divided by the input to a circuit or amplifier
What is the primary purpose of an amplifier?
Amplify a small signal or increase the gain
The arrow in the schematic diagram of a bipolar junction transistor points at...
1-collector 2-base 3-"N" type material in transistor
The arrow points to the part of the transistor that is doped with the "N" type material.
DC current can pass through a capacitor.
T/F
False, only AC current passes through capacitors
What do the initials JFET stand for?
Junction Field Effect Transistor
An SCR rated at 50 amps is the same physical size as an SCR rated for 5 amps.
T/F
False, the higher the ampacity of the SCR, the larger the physical size of the SCR
An Analog signal is an output from a device that can vary anywhere between a low value and a high value. (i.e., anything between 4 ma and 20 ma)
T/F
True, this signal can have numerous values
Cascading amplifiers or multistage amplifiers are when the output of one amplifier is connected to the input of another amplifier. T/F
True, cascading amplifiers can provide more gain than a single stage amplifier
Common Gate, Common Source and Common Drain are three common configurations for a JFET transistor
T/F
True. These configurations are similar to the Common Base, Common Emitter and Common Collector configurations in a Bi-Polar Junction Transistor
How do you change the speed of an AC induction motor?
The speed of an AC induction motor is changed by changing the frequency of the applied power source. This is usually done with a VFD (variable speed drive)
What is the most common cause of solid state device failures?
1-overvoltage 2-excess current 3-overheating
Overheating is the most common cause for failures. Heat sinks, forced air cooling are methods used to minimize overheating.
If the A input on a OR gate is 1, and the B input is zero, What will the output be?
Since this is an OR gate, if either one of the inputs is a 1 (or High), the output will be a 1 (or High)
The speed of a DC motor is changed by adjusting the applied voltage to the motor.
T/F
True, the speed is proportional the the applied voltage.
A silicone controlled rectifier SCR is also known as a Thyristor
T/F
True, a thyristor is the same thing as an SCR