Electronic Devices and Circuits Study Notes, Exams of Physics

Download Electronic Devices and Circuits Study Notes and more Exams Physics in PDF only on Docsity! CETa Study Guide with Correct Answers. 8.33 meters is the full wavelength in air for what RF frequency? Answer - 36 MHz Decimal 164 would appear as what in binary? Answer - 10100100 A resistor has color stripes yellow, violet, violet, silver. It is? Answer - 470 MegOhm +/- 10% What is the total capacitance of three capacitors valued at 100uf, 100uf and 50uf when connected in series? Answer - 25 pf What is the ripple frequency of a full wave single phase bridge rectifier operated at 60 Hz? Answer - 120 Hz What emits a voltage when heated or cooled? Answer - Thermocouple Adding the binary numbers 101011 and 001110 will give you what result? Answer - 111001 A component that reduces in resistance as it is heated. Answer - A negative temperature coefficient thermistor An autotransformer Answer - has a single winding A dual trace oscilloscope differs from a single trace in that only the dual trace scope: Answer - alternates sweeps If an RF signal Voltage is reduced by 6db it is then : Answer - half the original size Applying positive voltage to the P end and negative to the N end of a germanium diode: Answer - will forward bias it You would probably prefer a digital VOM over an ordinary analog meter: Answer - for most accuracy You should expect the video amplifier in a radar or TV receiver to have a frequency response of: Answer - 0-6 MHzd The radio communication mode that utilizes the basic frequency and one of the side bands: Answer - is called "SSB" When using fiber optic to transfer a signal, the light must: Answer - enter the "cone of acceptance" The energy stored in a coil is measured in: Answer - Henrys The telephone communication term "Cellular" refers to: Answer - small geographic areas covered by each base station Integrated circuit failures often exhibit: Answer - open or short conditions Which of these would you normally choose to cause an LED to light? Answer - 3 VDC A capacitor (3/8"x1/8" ceramic or mica) marked 47K is: Answer - 47 pf +/- 10% A "digital storage oscilloscope": Answer - uses micro processing and memory to allow close analysis of signal. Carbon microphones are much like variable: Answer - resistors An antenna that is longer than another: Answer - will have a lower resonant frequency An 8 bit binary code allows how many logical combinations. Answer - 256 An inductor in an electronic circuit: Answer - resists AC current flow A printer directly connected to a personal computer would use what kind of connection? Answer - usb or parallel centronics The digital method of representing characters by using combinations of zeros and ones is called: Answer - Binary AM utilizes signal level variations where FM utilizes : Answer - Frequency variations What decimal number is represented by the binary number 01101010? Answer - 106 Decimal 50 would appear as what number in Hex? Answer - 32 The display of a DMM would probably be: Answer - LCD A disadvantage of LCD is: Answer - Environmental temperature sensitivity A series DC motor with no load: Answer - maybe damaged by excessive speed Which motor maintains a constant speed with changing load? Answer - Shunt A small power drill or electric mixer would probably be powered by a Answer - Series Motor 0 db when referring to audio signals means: Answer - decibels referenced to 1 milliwatt Sideband frequencies are produced when an radio carrier frequency is: Answer - modulated Doubling the power in a transmitter output is a: Answer - 3 db gain 0 db is what level of received TV signal? Answer - 1000 microVolts A byte is: Answer - 8 bits In a 3 input AND gate: Answer - 3 input must be high for a high output An LCD operates by polarizing the light through filters. The fluid rotates the light: Answer - 90 degrees To test an SCR with an ohmmeter. Answer - with + to anode and - to cathode, short gate and anode together Using the Rx100 range and testing between the source and drain of an N channel JFET: Answer - readings should be equal in both directions With + voltage to drain or source and a - voltage to the gate on an N channel JFET, internal resistance of the JFET will be: Answer - High Which is least likely to cause ESD damage to MOSFET Answer - flux A logic probe: Answer - indicates high and low voltage conditions In a typical electrical generator a small DC voltage applied to the field windings: Answer - is able to control the output level of the generator When working with and testing lead acid batteries Answer - Always wear eye protection and never cause a spark Audio signals, such as the output from DVD players, satellite receivers and preamplifers, usually are of what amplitude for input to a TV, modulator or other equipment? Answer - 1 voltage peak to peak Which of these signal parameters does a spectrum analyzer show? Answer - Magnitude and frequency Permanent, non-volatile, non removable data storage in a computer is: Answer - ROM What should be used first to clean a corroded plated soldering iron tip? Answer - flux, cloth and heating When soldering high voltage connections: Answer - Leave the terminal with a smooth and rounded covering of solder Class AB operation of an audio amplifier means that current flows through the active device(tube, transistor,FET,IC) for how many degrees of the input signal wave? Answer - more than 180 but less then 360 A track on a computer disk is: Answer - divided into sectors A PC has conventional RAM and ROM memory area(in a PC it is 0 to 640 kilobytes); upper memory area(640 kilobytes to 1 meg) and extended memory area(above 1 meg). What other names for internal memory types do PCs have? Answer - Tape Drive Which video system has the highest resolution? Answer - XVGA You would want to use a dual trace oscilloscope to measure: Answer - signal difference between two points Common Intermediate Frequencies(IF's) and FM commercial broadcast receivers are: Answer - 455 MHz and 10.7MHz Analog radio receiver signal compression: Answer - reduces the high frequency received signal amplitude Coaxial cable line losses at RF frequencies are due to: Answer - wire resistance, capacitive and inductive reactance You are troubleshooting audio reproduction equipment and measure the signal to be input into the audio amplifier. What approximate RMS level would you expect the signal to be? Answer - 1000 millivolts The noise level in a radio receiver is generated mostly in the: Answer - RF section The fast charging rate for a NiCad of Ni-Mh battery should not exceed: Answer - 10% of its AHr or ampere hour rating Which of the following in a PC would be part of disk operations? Answer - SATA or IDE controller An LED Answer - can be used as a fiber optic signal source A dual trace oscilloscope may have Answer - A Z input for intensity modulation The gain of an op-amp connected as an inverting amplifier is determined by the external Answer - feedback and input resistors Which propagation condition would be significant for a UHF signal to be received at a distance of 500 miles? Answer - Tropospheric ducting A three input NAND has two low inputs and one high input. The output is: Answer - High Which of these would be considered a component of a "basic" power supply? Answer - diode rectifier A "Video Signal" is defined as: Answer - baseband including visual information You are servicing a power supply and have disconnected power. It has several 250 uf capacitors connected in parallel. To avoid shock these capacitors: Answer - Should be discharged to chassis ground, through a suitable resistor A schematic used in electronic: Answer - is much like a road map for following signals High voltage should be discharged before servicing a product. After disabling AC input power, discharge a high voltage power source by: Answer - draining thru a large value resistor to chassis ground Which of these would be an important electrical consideration in the use of a transformer? Answer - The operating frequency If a 12v product is dissipating 50w, how much load resistance does the device represent? Answer - 2.9 ohms An "audio signal" is defined as: Answer - frequencies in the 20Hz to 15000Hz range What will cause a generator to produce DC voltage rather then AC? Answer - the commutator You suspect the unit has an internal short. To prevent further damage when you apply power, you should: Answer - insert a low resistance high wattage(100ohm, 10w) resistor in series with the power input. A ripple counter: Answer - Is two or more logical flip-flops connected sequentially with the input pulses toggling the first one When voltage is applied to a capacitor: Answer - current is maximum at first, then reduces as the capacitor becomes charges. An electrolytic capacitor in series between the power transformer and the rectifiers in a power supply: Answer - is part of a voltage doubler circuit Information travels through optic fiber via the flow of: Answer - photons You would most likely prefer an analog VOM over a DMM for: Answer - accuracy Which of these circuits would most likely use a zener diode? Answer - a power regulator A block in a digital diagram is called a NOR. Which is true? Answer - It is a NOT OR or Inverted OR A 10W signal is received at 5W. How many dB loss? Answer - 3 dB loss It is desired to raise the power to a speaker from 15W to 30. This is a: Answer - 3dB increase Which of these IC or semiconductor devices normally requires the most careful handling to avoid damage by static electricity? Answer - CMOS Which of these components most closely compares to the output of a solar cell? Answer - A NiCad battery Three series inductors have values of 20mh, 30mh and 40mh respectively total inductance is: Answer - 90mh Phototransistors: Answer - can be sensitive to invisible light To simplify the following of an electrical signal path through circuitry you could: Answer - use a block diagram AC power outlet strips with surge suppressors will include at least one: Answer - MOV Connecting 3 capacitors of .05uf, 20uf and 40uf in series results in a total capacitance of: Answer - .0498uf You would use the formula(Lt = L1+L2+L3): Answer - To find the total inductance in a series circuit The fifth color band on a 5% resistor is yellow. This tells you: Answer - its failure rate VHF or UHF antennas don't use waveguides as feed lines because: Answer - the large dimensions at these wavelengths make other trans lines more practical. To trace a logic path, you might use: Answer - A logic pulser Ordinary alpha numeric information transmitted by a computer is converted to binary using: Answer - an encoder In electronic devices what term refers to residual magnetism? Answer - Hysteresis Some variable capacitors are made so the plates interleave. The capacitance varies as the plates open(separate) and close. As they open: Answer - The capacitance decreases In VOM's voltage multiplier resistors are important: Answer - in the voltage scales In a series tuned circuit, to increase the resonant frequency, you would need to: Answer - decrease the inductance A mosfet: Answer - amplifies signal voltage variations Torroid cones are used in transformers for: Answer - concentrating the magnetic lines of flux A PLL or phase locked loop circuit, contains a VCO, or voltage controlled oscillator. The output of the VCO is an: Answer - AC changing frequency signal A variable capacitor depends on: Answer - the plate separation being adjustable While anode and cathode voltages are maintained the gate level in an SCR drops below the trigger point. What happens? Answer - The SCR stays on The combination of resistance and reactance which restricts the flow of alternating current is called: Answer - Impedance The output of a thermocouple would most likely be measured in: Answer - millivolts The Z axis on an oscilloscope is: Answer - intensity When soldering transistor or IC chip legs. What should be used to prevent overheating of the small discrete components/ Answer - heat sink clip Which of the below would normally be used for the core of a transformer? Answer - Ferrite The '1' in binary number 100000 carries a weight of: Answer - 32 You would choose an LCD if you needed: Answer - a low current digital display Germanium diodes: Answer - normally drop about .3V with forward current RF signal propagation that is normally considered "live of sight" would be: Answer - UHF