Milestones in Electronics (Floyd and Chattopadhyay)

• 1838 - telegraph - Samuel F. B. Morse
  

• 1844 - wireless telegraphic communications
• 1864 - James Clerk Maxwell proposed EM wave theory
  
• 1876 - Alexander Graham Bell demonstrated the first voice transmission
  
• 1879 - light bulb - Thomas Edison: discovered diode effect while working with VT
• 1888 - Heinrich Hertz experimented on detection of EM radiation; he published the results in the paper entitled on electromagnetic waves in air and their reflection.
  
• 1889 - first electromechanical telephone switching machine
• 1896 - Sir J. C. Bose developed devices to generate, radiate, and receive millimeter waves.
  
• 1897 - electron, CRT - Sir Joseph John Thomson
• 1901 - patent for experimental setup of Reginald Fessenden for AM
• 1906 - Christmas, first wireless radio broadcast - Fessenden, Brant Rock, MA

• 1904 - Fleming valve: vacuum tube in one direction - John A. Fleming
• 1907 - audiotron: tube with added grid that can amplify signals - Lee De Forest
• 1912 - radio amateur in San Jose, California was able to broadcast music.
• Regenerative amplifier - invented by Edwin Armstrong.
• Oscillator - invented by Lee De Forest.
• 1918 - Multivibrator was invented by Eccles-Jordan.
  

• 1921 - the secretary of commerce, Herbert Hoover, issued the first license to a broadcast radio station;

superheterodyne - invented by Edwin Armstrong solved the problem for high frequency communications

• 1923 - first TV picture tube iconoscope - Vladimir Zworykin (USA)
• experimental demonstration of single sideband AM - R. A. Heising
• 1925 to 1927 - J. L. Baird demonstrated actual TV (Britain)
  
• 1926 - pentode - Bernard D. H. Tellegan
  
• 1927 - patent for the first complete TV system - Philo T. Farnsworth
• negative feedback - invented by Harold S. Black, Bell Laboratories
• 1929 - pentode was introduced commercially
  
• 1930s - development in radio, metal tubes, AGC, midget radios, directional antenna, etc.
• FM - Edwin Armstrong (USA)
  
• 1937 - John Atanasoff of Iowa State University envisioned a machine that can do complex math works

• 1939 - Atanasoff and student Clifford Berry constructed binary machine called ABC (Atanasoff-Berry Computer)
• ABC used VT for logic and capacitor for memory

• magnetron: a microwave oscillator - Henry Boot and John Randall (Britain)

• klystron tube - Russell and Sigurd Varian, Stanford University (USA)

• 1940s - radar and VHF comm were made possible by magnetron and klystron
• 1946 - ENIAC: first stored program computer - John von Neumann, University of Pennsylvania
• 1947 - transistor - Walter Brattain, John Bardeen, William Shockley
• printed circuits were invented
• 1948 - 604 types - IBM
  
• 1950 - Colour TV was adopted in US
• Ebers developed SCR or thyristor
  

First world-wide TV was made possible by TELSTAR satellite.

• 1951 - commercial manufacturing of transistors
• JFET - proposed by William Shockley
• 1954 - MASER - Charles H. Townes
  
• 1958 - September 12, integrated circuit - Jack Kilby, Texas Instruments
• Tunnel diode - L. Esaki
  

• 1960s - precursors to the Internet began, ARPANET
• LASER
  
• 1960 - first MOSFET - announced by Kahng and Attla, Bell Laboratories
• 1961 - digital IC - Buie, Pacific Semiconductor
  
• 1965 - muA709, first successful op-amp, - Bob Widlar, Fairchild Semiconductor; this design suffered from latch-up
• The 741, also from Fairchild solved the problem.
• IMPATT - Johnston, DeLoach, and Cohen
• 1966 - proposals of light communication via optical fiber - Kao and Hockham, Werts
  
• 1969 - CCD (charge-coupled device) - Willard Boyle and George Smith, Bell Laboratories
  

Octopus system - 100 terminals on a computer - Lawrence Livermore, National Laboratory

• 1970s - introduction to pocket calculators and optical ICs
• 1970 - BJT-based RAM
  
• 1971 - Intel was formed by a group from Fairchild. 4004 chip was introduced.
• Ted Hoff - designed 4-bit microprocessor at Intel Corp.
  

• 8008 - the first 8-bit microprocessor
• 1973 - MOS-based RAM
• 1974 - Intel 8080 - first general purpose microprocessor

Intel 80286/386/486 - 32-bit CPUs

***Computer Generations:
1st - valve-based
2md - transistor-based
3rd - IC-based
4th - VLSI architecture-based

• 1975 - first personal computer, by Altair, featured by Popular Science in January
  
• 1977 - LASER diodes using AlGaAs
  
• 1978 - 64kB RAM chip
• 1979 - Intel 8088 - 16-bit microprocessor
  
• 1980s - cable hookups
• 1990s - wide application of the Internet, e-commerce
• 1990 - world-wide web - Tim Berness-Lee
  
• 1993 - 130 websites
• 1995 - FCC alloted spectrum space for Digital Audio Radio Service
• 1996 - FCC adopted digital TV standards
  
• 2001 - 24 million websites

Microprocessor Quiz 2

Identification.

1. The designer of 555 timers.

2. Any device that stores the status of something at a given time and can operate on input to change the status and or cause an action or output to take place for any given change.

3. Used as simplest form of error-detecting device.

4. The binary medium of communication with a computer through a designed set of instructions specific to each computer.

5. A miniaturized electronic circuit (consisting mainly of semiconductordevices, as well as positive components) that has been manufactured in the surface of a thin substrate of semiconductor material.

6. The main reason for inventing the World's forst comuter, Colossus.

7. A Japanese company that owned the rights for the first microprocessor.

8. A device or program that translates encoded data into its original format (e.g., it decodes the data).

9. They produced the first stored program computer, the first floating point machine, the first transistor computer, and the first computer to use virtual memory.

10. The designer of Intel 4004.

11. The other term for microprocessors.

12. The processor that allowed computers to more easily incorporate "real-world" data such as speech, sound, handwriting, photographic images.

13. A measure of computer's speed.

14. Microprocessor designed for gaming.

15. Microprocessor designed for MID (mobile internet devices).

16. A special purpose register that can move the bits of the word it holds left or right.

17. A special purpose register that holds an m-bit word.

18. A notation used in digital system which is equivalent to 4-bits.

19. A notation used in digital system which is equivalent to 16-bits.

20. A character-encoding scheme that represents text in computers, communications equipment, and other devices that use text.

Microprocessor Quiz

1. It is an electronic circuit that can store one bit of information.

2. It is an electronic circuit that can store one bit of memory.

3. Transparency is one of the characteristics of latches and flip-flops. This term denotes
the capability of storing and transferring information
the ability to control two or more signals
the capability to determine their output states whether it is in no change or in race condition
the ability to change at the transition of a clock signal

4. The T flip-flop is useful in constructing various types of:

5. It is the simplest example of even-parity checking:

6. These are devices that generate output based on a given input and/or a state using actions.

7. It was Intel's first microprocessor:

8. This is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles, or domains, each of which stores one bit of data.

9. This is a a form of computer memory, similar to core memory, formed by wrapping or closing magnetic tape around a current-carrying wire.

10. It is a programmable device used to implement combinational logic circuits.

11. It is a programmable logic device with a fixed OR array and a programmable AND array.

12. It was the first general purpose electronic computer.

13. It was also manufactured as a standalone microcontroller with various configurations of on-chip RAM and EPROM.

14. IBM selects this microprocessor for their PC, introduced in August, 1981.

15. It was a 32-bit chip microprocessor and was "muti-tasking", meaning it could run multiple programs at the same time.

16. It is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations.

17. It is the first 8-bit microprocessor.

18. 256 base 10 to BCD?

19. 27.35 base 16 to BCD?

20. 10011 base 2 to DEC?

21. 2132 base 5 to DEC?

22. On ASCII Table, 32 base 10 represents what character?

23. It is a measure of the ability of a logic gate output, implemented electronically, to drive a number of inputs of other logic gates of the same time.

24. It is the length of time starting from when the input to a logic gate becomes stable and valid, to the time that the output of that logic is stable and valid.

25. How many bits will you need to produce a 64K address space?

26. Which of the following is a desktop processor?
Xeon DP, Quad-core
Xeon MP, Eight-core
Itanium
Core 2 Quad

27. The first company to introduce 64-bit microprocessor to the market.

28. Which of the following microprocessors is manufactured by using CMOS technology?
Motorola 68030
IBM Power 1
Intel Pentium Pro
AMD K6

29. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital circuits.

30. It is a computer system technique developed, which goves an application program the impression that it has contiguous working memory (an address space), while in fact it may be physically fragmented and may even overflow on to disk storage.

Gibilisco Quiz 2

1. A positive electric pole:
A. Has a deficiency of electrons.
B. Has fewer electrons than the negative pole.
C. Has an excess of electrons.
D. Has more electrons than the negative pole

2. An EMF of one volt:
A. Cannot drive much current through a circuit.
B. Represents a low resistance.
C. Can sometimes produce a large current.
D. Drops to zero in a short time.

3. A potentially lethal electric current is on the order of:
A. 0.01 mA.
B. 0.1 mA.
C. 1 mA.
D. 0.1 A.

4. A current of 25 A is most likely drawn by:
A. A flashlight bulb.
B. A typical household.
C. A power plant.
D. A clock radio.

5. A piece of wire has a conductance of 20 siemens. Its resistance is:
A. 20 Ω.
B. 0.5 Ω.
C. 0.05 Ω.
D. 0.02 Ω.

6. A resistor has a value of 300 ohms. Its conductance is:
A. 3.33 millisiemens.
B. 33.3 millisiemens.
C. 333 microsiemens.
D. 0.333 siemens.

7. A mile of wire has a conductance of 0.6 siemens. Then three miles of the same
wire has a conductance of:
A. 1.8 siemens.
B. 1.8 Ω.
C. 0.2 siemens.
D. Not enough information has been given to answer this.

8. A 2-kW generator will deliver approximately how much current, reliably, at 117
V?
A. 17 mA.
B. 234 mA.
C. 17 A.
D. 234 A.

9. A circuit breaker is rated for 15 A at 117 V. This represents approximately how
many kilowatts?
A. 1.76.
B. 1760.
C. 7.8.
D. 0.0078.

10. You are told that a certain air conditioner is rated at 500 Btu. What is this in
kWh?
A. 147.
B. 14.7.
C. 1.47.
D. 0.147.

11. Of the following energy units, the one most often used to define electrical
energy is:
A. The Btu.
B. The erg.
C. The foot pound.
D. The kilowatt hour.

12. The frequency of common household ac in the U.S. is:
A. 60 Hz.
B. 120 Hz.
C. 50 Hz.
D. 100 Hz.

13. Half-wave rectification means that:
A. Half of the ac wave is inverted.
B. Half of the ac wave is chopped off.
C. The whole wave is inverted.
D. The effective value is half the peak value.

14. In the output of a half-wave rectifier:
A. Half of the wave is inverted.
B. The effective value is less than that of the original ac wave.
C. The effective value is the same as that of the original ac wave.
D. The effective value is more than that of the original ac wave.

15. In the output of a full-wave rectifier:
A. The whole wave is inverted.
B. The effective value is less than that of the original ac wave.
C. The effective value is the same as that of the original ac wave.
D. The effective value is more than that of the original ac wave.

16. A low voltage, such as 12 V:
A. Is never dangerous.
B. Is always dangerous.
C. Is dangerous if it is ac, but not if it is dc.
D. Can be dangerous under certain conditions.

17. Which of these can represent magnetomotive force?
A. The volt-turn.
B. The ampere-turn.
C. The gauss.
D. The gauss-turn.

18. Which of the following units can represent magnetic flux density?
A. The volt-turn.
B. The ampere-turn.
C. The gauss.
D. The gauss-turn.

19. A ferromagnetic material:
A. Concentrates magnetic flux lines within itself.
B. Increases the total magnetomotive force around a current-carrying wire.
C. Causes an increase in the current in a wire.
D. Increases the number of ampere-turns in a wire.

20. A coil has 500 turns and carries 75 mA of current. The magnetomotive force
will be:
A. 37,500 At.
B. 375 At.
C. 37.5 At.
D. 3.75 At.

Electronics Review Series 3 (10 Questions)

1. How much power does an electronic equipment consume, assuming a 5.50-A current flowing and a 120-V power source?
Solution: P = EI = (120)(5.5)
Ans. 660-W

2. Which of the following characterizes CMOS logic?
bipolar FETs
P-channel FETs
N-channel FETs
both P-channel and N-channel FETs
Ans. both P-channel and N-channel FETs

3. What refers to the form of DC motor with common field coils for both motor and generator?
Ans. dynamotor

4. What device stays on once triggered and stores one of two conditions as a digital circuit?
Ans. latch

5. ___ is a user program that has the ability to move a robot axis to any position within its range.
Ans. point-to-point

6. Find the flux density in gauss having a flux of 20,000-Mx having a perpendicular area of 2-cm^2.
Solution: 20000/2
Ans. 10,000 gauss

7. A software that converts a high level language program into machine or assembly language program:
Ans. compiler

8. A SAW device has electrodes that are desbcribed as:
Ans. interdigital

9. What is the cause of parallax error in analog-type meter?
Ans. reading the meter at an angle

10. Which semiconductor material is commonly used in the construction of LEDs?
Ans. gallium arsenide

Electronics Review Series 2 (20 Questions)

1. The knee voltage of a diode is approximately equal to:
Ans. barrier potential

2. What do you call the flux that does not follow the intended path in a magnetic circuit?
Ans. leakage flux

3. The ratio between the primary and the secondary currents in a transformer does not depend on:
Ans. nature of the core

4. Which is NOT part of CRT of oscilloscope?
aquadag coating
deflection plate
digital panel meter
electron gun
Ans. digital panel meter

5. An amplifier with an input resistance of 600 ohms has an input current of 500 microamperes. It delivers 100 milliampere to a 1000 ohm load. Calculate the dB gain of the amplifier.
Solution: 10log(Pout/Pin) = 10log((1k*100m^2)/(600*500u^2))
Ans. 48.24-dB

6. How many silver-zinc cells in series are needed for a 9-V battery?
Ans. 6

7. Which meter uses a dual triode tube and requires external power for operation?
Ans. VTVM

8. What is the most available LED color?
Ans. red

9. What term is used for an energy stored in an electromagnetic or electrostatic field?
Ans. potential energy]

10. What is the reciprocal of capacitance?
Ans. elastance

11. What is th input voltage of a carbon zinc cell?
Ans. 1.5-V

12. How does a conductor behave at absolute zero temperature?
Ans. as a superconductor

13. The attraction or repulsion between two magnetic poles is directly proportional to their strengths:
Ans. Coulomb's First Law

14. A half adder can be constructed using a/an:
Ans. XOR and AND gates

15. What is a thin layer in a PCB which is bounded to an insulating base material?
Ans. substrate

16. A window comparator requires how many op-amps?
Ans. 2

17. What refers to the hardware data entry and entry points of a microcomputer?
Ans. ports

18. What term is used in electronic measuring devices when a metal increases resistance due to heat produced by current flowing through them?
Ans. positive temperature coefficient

19. What oscillator operates on the principle of velocity modulation and changing the speed of electron passing through the tube?
Ans. Klystron

20. Which of the following ICs contain the most gates?
LSI
MSI
SSI
VLSI
Ans. VLSI

Coaching Notes Elex 1

Robot	Coined by Karel Capek
Power factor	True power / apparent power
Cray 1	First supercomputer; 1976; $ 7.5M
Shunt regulator	Load on the unregulated source should be kept constant
Flux and speed	Determine the voltage in DC generator
Lenz’s law	The directon of the generated V in a coil is such that it tends to produce I flow opposing a change of flux
Polarization of coil	Caused by formation of hydrogen on its positive plates
Plug fuse	10- to 15-A; <= 125-V
Iron-vane meter	Works on the principle of repulsion
Viltage regulator	Fields R and I are controlled
Short-coil	Detected by low resistance and overheat coil
Electronic oscillator	Amplifier with feedback
Bistable multivibrator	Can be used as frequency divider
Advantage of compiler over interpreter	The object can be stored and reused as often as required
Transputer	- Called “computer on a chip” - A 32-bit device - Based on parallel processing technique
Solids	Have maximum of 6 degrees of freedom
Telephone lines	75 ohms surge impedance

Electronics Review Series 1 (41 Questions)

1. Distance between the rotor and ... is called:
Ans. slip

2. 25-uH and 10-pF in parallel, what is the frequency?
Solution: f = 1/(2pi(sqrt(LC))) = 1/(2pi(sqrt(25u*10p)))
Ans. 10.1-MHz

3. What is the main consideration in the output stage of amplifiers?
Ans. power gain

4. 100010010111 base 2 -> DEC
Ans. 897

5. As magnetic intensity decreases, relative permeability of a magnetic material:
Ans. increases

6. When an SCR is compared to a switch, it is considered as ___ switch:
Ans. unidirectional

7. A standalone solar power system uses:
Ans. solar power and battery

8. An input signal that can activate or disable a gate:
Ans. strobe

9. a temperature coefficient of resistance of electrolytes:
Ans. negative

10. A type of secondary cell that can be recharged but with an electrolyte that cannot be refilled:
Ans. sealed rechargeable cell

11. Which of the following is a paramagnetic material?
carbon
copper
bismuth
oxygen
Ans. oxygen

12. B2F base 16 -> octal
Ans. 5457

13. CMOS means
Ans. complementary metal-oxide semiconductor

14. Which VT can be used for high frequency amplification?
Ans. pentode

15. If F = xy + x'y', Boolean expression is said to be implemented using decoders and OR gates, the connection involves:
Ans. 2 to 4 line decoders with 1 OR gate

16. Refers to the magnetic lines of force:
Ans. flux

17. With PNP voltage divider bias, you must use:
Ans. negative power supplies

18. A good conductor has how many valence electrons?
Ans. 1

19. A technique used to eliminate the need for inductive elements in monolithic integrated circuits:
Ans. RC synthesis

20. A multi-stage amplifier uses at least how many transistors?
Ans. 2

21. Which of the following is a DC bridge that is very useful for making extremely accurate voltage measurements?
Wheatstone bridge
potentiometer bridge
Kelvin bridge
Owen bridge
Ans. potentiometer bridge

22. What is meant by interfacing in computer systems?
Ans. synchronization od digital information transmission in computer and I/O external device

23. Mass of proton or neutron is ___ times of an electron:
Ans. 1,836

24. Class of mass memory devices that uses a laser beam to write or read onto a specified coated disk:
Ans. optical disk memory

25. What is the total effective capacitance of two 0.25-uF capacitors connected in series?
Solution: 0.25^2 + 0.25^2
Ans. 0.125-uF

26, An open inductor has __ resistance and __ inductance:
Ans. infinite R and zero L

27. When the gas pressure in the gas-filled diode is increased, its PIV rating:
Ans. decreases

28. Which of the following has the lowest dielectric strength?
glass
paper
mica
teflon
Ans. paper

29. Approximate mass of neutron at rest:
Ans. 1.6726 x10^-27 grams

30. Given L = 3-uH; C = 40-pF; what is the frequency in series?
Solution: f = 1/(2pi(sqrt(3u*40p)))
Ans. 14.5-MHz

31. An inductive circuit of resistance 16.5 ohms and inductance of 0.14-H takes a current of 25-A. If the frequency is 50-Hz, find the supply voltage.
Solution: Z = sqrt(R^2 + (2pi(fL))^2)
Z = 46.9755 ohms
V = ZI = 46.9755(25)
Ans. 1174.39-V

32. What is the advantage of a pentode tube over a triode?
Ans. less control grid-to-plate capacitance

33. This occurs in PN diode when the electric field in the depletion layer increases to the point where it can break covalent bonds and generate electron hole pairs.
Ans. Zener breakdown

34. A vacuum tube will conduct only if its plate is ___ with respect to cathode.
Ans. positive (+)

35. An amplifier with 85% efficiency is likely to be:
Ans. class C

36. The pointer of an indicating instrument is generally made of:
Ans. aluminum

37. What will happen to an atom if an electron is either taken out or taken into the same atom?
Ans. becomes an ion

38. What is the next binary number following 10111 base 2 in the counting sequence?
Ans. 11000

39. The ratio between the active power and the apparent power of a load in an AC circuit is called:
Ans. power factor

40. Transmit time is the time taken by the electrons or holes to pass from:
Ans. emitter to collector

41. A resistor wound with a wire doubled back on itself to reduce the inductance is referred to as:
Ans. bifiliar resistor

DC Metering

A "movement" is the display mechanism of a meter.

D'arsonval and Weston - common polarity-sensitive meter designs, PMMC (permanent magnet moving coil) meter movement

Galvanometer - The first meter movements built.

Electrostatic meter movement - used for
measuring ver high voltage because of high resistance.

CRT - uses polarity-sensitive meters, because of deflection and reversal of electrons at either positive or negative side of the tube

CRT contains two pairs of deflection plates rather than just one

------------
FULL SCALE INDICATION:

In electromagnetic movements - "full-scale deflection current" is necessary to rotate the needle so that it points to the exact end of the indicating scale.

In electrostatic movements - the full-scale rating will be expressed as the value of voltage resulting in the maximum deflection of the needle actuated by the plates, or the value of voltage in a cathode-ray tube which deflects the electron beam to the edge of the indicating screen.

In digital movements - it is the amount of voltage resulting in a "full-count" indication on the numerical display: when the digits cannot display a larger quantity.

------------

Electromagnetic movements work on the principle of a magnetic field being generated by electric current through a wire. Examples of electromagnetic meter movements include the D'Arsonval, Weston, and iron-vane designs.

Electrostatic movements work on the principle of physical force generated by an electric field between two plates.

Cathode Ray Tubes (CRT's) use an electrostatic field to bend the path of an electron beam, providing indication of the beam's position by light created when the beam strikes the end of the glass tube.

------------
Part 2

Extended voltmeter ranges are created for sensitive meter movements by adding series "multiplier" resistors to the movement circuit, providing a precise voltage division ratio.

------------
Part 3 VOLTMETER

Loading effect - present to some degree in every instance of voltmeter usage

Potentiometric or null-balance instrument - a final solution to voltmeter loading;
uses null detector or potentiometer to compare voltages

Null detector - a very sensitive device that can detect very small changes in voltage

• An ideal voltmeter has infinite resistance.
• Too low of an internal resistance in a voltmeter will adversely affect the circuit being measured.
• Vacuum tube voltmeters (VTVM's), transistor voltmeters, and potentiometric circuits are all means of minimizing the load placed on a measured circuit. Of these methods, the potentiometric ("null-balance") technique is the only one capable of placing zero load on the circuit.
• A null detector is a device built for maximum sensitivity to small voltages or currents. It is used in potentiometric voltmeter circuits to indicate the absence of voltage between two points, thus indicating a condition of balance between an adjustable voltage source and the voltage being measured.

----------
Part 4 AMMETER

• Ammeter ranges are created by adding parallel "shunt" resistors to the movement circuit, providing a precise current division.
• Shunt resistors may have high power dissipations, so be careful when choosing parts for such meters!
• Shunt resistors can be used in conjunction with high-resistance voltmeters as well as low-resistance ammeter movements, producing accurate voltage drops for given amounts of current. Shunt resistors should be selected for as low a resistance value as possible to minimize their impact upon the circuit under test.

Clamp-on ammeter - makes safe and quick current measurements, because it introduces no internal resistance to the circuit under test.

Hall-effect sensor - small magnetic field detector used in modern designs of clamp-on ammters to accurately determine field strength.

• An ideal ammeter has zero resistance.
• A "clamp-on" ammeter measures current through a wire by measuring the strength of the magnetic field around it rather than by becoming part of the circuit, making it an ideal ammeter.
• Clamp-on meters make for quick and safe current measurements, because there is no conductive contact between the meter and the circuit.

----------
Part 5 OHMMETER

Requirements:

*Internal source of voltage - to create the necessary current to operate the movement
*Appropriate ranging resistors - to allow just the right amount of current through the movement at any given resistance

Ohmmeters only function correctly when measuring resistance that is not being powered by a voltage or current source.

The ohmmeter's accurate indication depends on the only source of voltage being its internal battery.

• Ohmmeters contain internal sources of voltage to supply power in taking resistance measurements.
• An analog ohmmeter scale is "backwards" from that of a voltmeter or ammeter, the movement needle reading zero resistance at full-scale and infinite resistance at rest.
• Analog ohmmeters also have nonlinear scales, "expanded" at the low end of the scale and "compressed" at the high end to be able to span from zero to infinite resistance.
• Analog ohmmeters are not precision instruments.
• Ohmmeters should never be connected to an energized circuit (that is, a circuit with its own source of voltage). Any voltage applied to the test leads of an ohmmeter will invalidate its reading.

----------

Potentiometer

POTENTIOMETER

wiper - potentionmeter movable element

voltage divider - used in electric meter circuits

potentiometer - uses VDB

slidewire - the resistive strip of material in potentiometer

2 types:
linear
rotary

potentiometer division ratio - a function of resistance, and not the voltage applied

POTENTIAL (voltage) meter (control)

Gibilisco Quiz 1

1. The atomic number of an element is determined by:

A. The number of neutrons.

B. The number of protons.

C. The number of neutrons plus the number of protons.

D. The number of electrons.

2. The atomic weight of an element is approximately determined by:

A. The number of neutrons.

B. The number of protons.

C. The number of neutrons plus the number of protons.

D. The number of electrons.

3. Suppose there is an atom of oxygen, containing eight protons and eight

neutrons in the nucleus, and two neutrons are added to the nucleus. The resulting

atomic weight is about:

A. 8.

B. 10.

C. 16.

D. 18.

4. An ion:

A. Is electrically neutral.

B. Has positive electric charge.

C. Has negative electric charge.

D. Might have either a positive or negative charge.

5. An isotope:

A. Is electrically neutral.

B. Has positive electric charge.

C. Has negative electric charge.

D. Might have either a positive or negative charge.

6. A molecule:

A. Might consist of just a single atom of an element.

B. Must always contain two or more elements.

C. Always has two or more atoms.

D. Is always electrically charged.

7. In a compound:

A. There can be just a single atom of an element.

B. There must always be two or more elements.

C. The atoms are mixed in with each other but not joined.

D. There is always a shortage of electrons.

8. An electrical insulator can be made a conductor:

A. By heating.

B. By cooling.

C. By ionizing.

D. By oxidizing.

9. Of the following substances, the worst conductor is:

A. Air.

B. Copper.

C. Iron.

D. Salt water.

10. Of the following substances, the best conductor is:

A. Air.

B. Copper.

C. Iron.

D. Salt water.

11. Movement of holes in a semiconductor:

A. Is like a flow of electrons in the same direction.

B. Is possible only if the current is high enough.

C. Results in a certain amount of electric current.

D. Causes the material to stop conducting.

12. If a material has low resistance:

A. It is a good conductor.

B. It is a poor conductor.

C. The current flows mainly in the form of holes.

D. Current can flow only in one direction.

13. A coulomb:

A. Represents a current of one ampere.

B. Flows through a 100-watt light bulb.

C. Is one ampere per second.

D. Is an extremely large number of charge carriers.

14. A stroke of lightning:

A. Is caused by a movement of holes in an insulator.

B. Has a very low current.

C. Is a discharge of static electricity.

D. Builds up between clouds.

15. The volt is the standard unit of:

A. Current.

B. Charge.

C. Electromotive force.

D. Resistance.

16. If an EMF of one volt is placed across a resistance of two ohms, then the

current is:

A. Half an ampere.

B. One ampere.

C. Two amperes.

D. One ohm.

17. A backwards-working electric motor is best described as:

A. An inefficient, energy-wasting device.

B. A motor with the voltage connected the wrong way.

C. An electric generator.

D. A magnetic-field generator.

18. In some batteries, chemical energy can be replenished by:

A. Connecting it to a light bulb.

B. Charging it.

C. Discharging it.

D. No means known; when a battery is dead, you have to throw it away.

19. A changing magnetic field:

A. Produces an electric current in an insulator.

B. Magnetizes the earth.

C. Produces a fluctuating electric field.

D. Results from a steady electric current.

20. Light is converted into electricity:

A. In a dry cell.

B. In a wet cell.

C. In an incandescent bulb.

D. In a photovoltaic cell.