ot10.07.18(elecs)

A 4-layer diode turns on when the anode-to-cathode voltage exceeds A. the forward-breakover voltage B. the forward-blocking voltage C. 0.7V D. the gate voltage

A

A class-A circuit would not work well as: A. a television transmitter PA B. a stereo hi-fi amplifier C. a low-level microphone preamplifier D. the first stage in radio receiver

A

A defect than can be described as a pair of vacant lattice sites, an anion site and a cation site. A. Schottky defect B. planer defect C. line defect D. Frenkel defect

A

A gain of -15dB in the circuit means A. The input signal is stronger than the output B. the output signal is stronger than the input C. the input signal is 15 times as stronger as the output D. the output signal is 15 times as stronger as the input

A

A hot-wire ammeter: A. can measure ac as well as dc B. can indicate very low voltages C. measure electrical energy D. works only when current flows in one direction

A

As the number of turns in a coil increases, the reactance: A. increases B. decreases C. stay the same D. is stored on the core material

A

Calculate the harmonic distortion components for an output signal having fundamental amplitude of 2.1V, second harmonic amplitude of 0.3V, third harmonic component of 0.1V, and fourth harmonic component of 0.05V A. 14.3%,4.8%,2.4% B. 14.3%,4.2%,2.8% C. 12.3%,4.8%,2.4% D. 12.3%,4.2%,2.8%

A

Drain current in the constant-current region increases when A. the gate-to-to-source bias voltage decreases B. the gate-to-source bias voltage increases C. the drain-to-source voltage increases D. the drain-to-source voltage decreases

A

For a certain magnetic material, the ___ the area inside the hysteresis loop, the __ the hysteresis losses. A. greater, larger B. smaller, larger C. greater, smaller D. smaller, smaller

A

For a parallel AC circuit, ___ is used as a reference phasor. A. voltage B. power C. current D. resistance

A

For a series AC circuit, ___ is not used as a reference phasor. A. voltage B. impedance C. current D. conductance

A

GaAs is a/an A. compound B. element C. conductor D. gas

A

If the capacitor has a negative temperature coefficient A. its value decreases as the temperature rises B. its value increases as the temperature rises C. its value does not change with temperature D. it must be connected with the correct polarity

A

Often used to characterize two-port networks such as amplifiers and filters, but they can be used on networks with an arbitrary number of ports. A. vector network analyzer B. spectrum analyzer C. vectorscope D. sweep generator

A

The PUT is A. trigger on and off by the gate-to-anode B. much like the UJT C. not a four-layer diode D. not a thyristor

A

The ac load line differs from the dc load line because A. the effective ac collector resistance is less than the dc collector resistance B. the effective ac collector resistance is less than the ac collector resistance C. the effective dc collector resistance is less than the dc collector resistance D. the effective ac collector resistance is greater than the dc collector resistance

A

The circuit has a resistance of 1000ohms in parallel with the capacitance of 1000pF. The frequency is 100kHz. If the wattmeter reads a VA power of 88 watts, what is the true power? A. 74.4 W B. 72.6 W C. 76.1 W D. 73.3 W

A

The current going into a point in a dc circuit always equal to the current: A. flowing out of the point B. delivered by the power supply C. through any one of the resistances D. at any other point

A

The magnetic field of a magnetized iron bar when strongly heated A. becomes weaker B. becomes stronger C. reverses in direction D. is unchanged

A

The meter movement in an illumination meter measures: A. Current B. Energy C. Voltage D. Power

A

The rms value is the same as the peak value of A. perfect square waves B. sawtooth waves C. perfect triangle waves D. perfect sine waves

A

What is the value of current below which the SCR switches from the conduction state to the forward blocking region under stated conditions? A. holding current B. forward current C. reverse current D. trigger current

A

Why is a two-pole magnetic field setup around a coil? A. because separate lines of magnetic force link and combine their effects B. because concentric lines of force cross at right angles and combine C. because lines of force are separated and bent at the coil ends D. because separate lines of force are attracted to the two poles of the coil

A

A certain bipolar transistor PA is 66 percent efficient. The output power is 33W. The dc collector power input is: A. 22W B. 50W C. 100W D. 2.2kw

B

A certain passive network has equivalent impedance Z=3+4i ohms and an applied voltage v=42.5cos(1000t+30deg)V. Determine the power factor. A. 0.6 lagging B. 0.6 leading C. 0.7 lagging D. 0.7 leading

B

A class A circuit would not work well as: A. a stereo hi-fi amplifier B. a television transmitter PA C. a low-level microphone preamplifier D. the first stage in the radio receiver

B

A device has a voltage gain of 23dB. The input voltage is 3.3V. The output voltage is: A. 76V B. 47V C. 660V D. 56V

B

A electric power line carries a current of 1400A in a location where the earth's magnetic field is 5.0x10^-5T. The line makes an angle of 75deg with respect to the field. Determine the magnitude of the magnetic force pm a 120-m length of line. A. 8.50N B. 8.11N C. 7.82N D. 8.66N

B

A frequency synthesizer makes use of A. the hexidecimal numbering B. a divider C. an or gate D. an octal numbering system

B

A p-channel MOSFET operating in the enhancement mode is characterized by Vt=-3V and Idq= -8 mA when Vgsq= -4.5V. Find Vgsq if Idq= -16mA. A. -0.80V B. -0.88V C. -0.94V D. -0.78V

B

A transformer has a secondary-to-primary turn ratio is 0.6. This transformer is: A. a step-up unit B. a step-down unit C. neither step-up and step-down circuit D. a reversible unit

B

Calculate the efficiency of a class B amplifier for a supply voltage of Vcc=24V with peak output voltages of Vl(p)=22V A. 90% B. 72% C. 87% D. 75%

B

Calculate the output voltage for resistor components of value Rf=470kohms, R1=4.3kohms, R2=33kohms and R3=33kohms for an input of 80uV. A. 1.23V B. 1.78V C. 2.11V D. 2.34V

B

If the ratio of Xc/R is 1, the phase angle is: A. 0deg B. -45deg C. -90deg D. 45deg

B

In Boolean algrebra, a high signal added to another low signal is A. 10 B. 1 C. 11 D. 0

B

In an N-channel JFET, pinchoff occurs when the gate bias is A. slightly negative B. very negative C. slightly positive D. zero

B

In negative-edge triggering, the change of state occurs when: A. the pulse level is high B. the pulse level is going high to low C. the pulse level is going from low to high D. the pulse level is low

B

In the voltage divider network, the total resistance A. should be large to minimize current drain B. should be as small as the power supply will allow C. is not important D. should be such that the current is kept to 100mA

B

It is a thin polished slice of semiconductor crystal on which integrated circuit can be fabricated often in duplicate, for cutting into individual slice. A. silicon B. wafer C. indium D. gallium

B

It is method of stabilizing the voltage gain. A. darlington pair B. swamping C. differential mode D. common mode

B

One of the other input can be true for the output to be false. A. AND B. NOR C. OR D. XNOR

B

The gain of a transistor in a common-emitter circuit is 100 at a frequency of 1000Hz. The gain is 70.7 at 335kHz. The gain drops to 1 to 210Mhz. The alpha cut-off is : A. 1kHz B. 335kHz C. 210kHz D. 70.7kHz

B

The input signal to a transistor amplifier results in saturation during part of the cycle. This produces: A. the greatest possible amplification B. reduced efficiency C. avalanche effect D. nonlinear output impedance

B

The major advantage of silicon-on-insulator are the following except: A. low diffusion capacitance B. higher diffusion capacitance C. lower dynamic power consumption D. nominals threshold voltage must be very high

B

The nine's complement of 3 is A. 8 B. 6 C. 3 D. 9

B

The term "semiconductor" arises from A. resistor-like properties of metal oxides B. variable conductive properties of some materials C. the fact that there's nothing better to call silicon D. insulator properties of silicone and GaAs

B

What maximum voltage can be applied across the capacitor for very short period of time? A. working voltage B. surge voltage C. stray voltage D. peak voltage

B

Which of the following is not a characteristic of mica capacitors? A. high efficiency B. small size C. capability to handle high voltages D. low loss

B

Which of the following with not cause a major error in an ohmmeter? A. a small voltage between points under test B. a small change in resistance to be measured C. a slight error in the range switch selection D. a slight change in switchable internal resistance

B

A 100-kVA transformer is at 80 percent of rated load at power factor 0.85 lagging. How many kVA in additional load at 0.60 lagging power factor will bring the transformer to full rated load? A. 21.8 kVA B. 22.2 kVA C. 21.2 kVA D. 22.4 kVA

C

A MOSFET differs from a JFET mainly because A. of the power rating B. the MOSFET has two gates C. the JFET jas a pn junction D. MOSFETs do not have a physical channel

C

A logic circuit has an output 0 when the input is 1 and vice versa. A. NOR gate B. OR gate C. NOT gate D. XOR gate

C

A semiconductor device with four alternating layers (P-N-P-N) taht are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action. A. SCR B. thyristor C. IGBT D. triac

C

A silicon power transistor is operated with a sink (0sa= 1,.5degC/W). The transistor, rated at 150W(25degC) has 0jc=0.5degC/W, and the mounting insulation has 0cs=0.6degC/W. What maximum power can be dissipated if the ambient temperature is 40degC and tjmax=200degC? A. 63.5W B. 57.5W C. 61.5W D. 58.2W

C

An SCR differs from the 4-layer diode because A. it is not a thyristor B. it does not have four layers C. it has a gate terminal D. it cannot be turned on and off

C

An oscillator might fail to start for any of the following reasons except: A. low power supply voltage B. low stage gain C. in-phase feedback D. very low output impedance

C

An unimportant factor concerning the frequency at which a P-N junction will work effective is: A. the type of semiconductor materials B. the cross-sectional area of the junction C. the reverse current D. the capacitor with reverse bias

C

CE amplifier is characterized by A. a low voltage gain B. moderate power gain C. signal phase reversal D. very high output impedance

C

Find the counter emf of a motor when the terminal voltage is 240V and the armature current is 50A. The armature resistance is 0.08ohms. The field current is negligible. A. 244V B. 240V C. 236V D. 232V

C

How can electrical currents be induced with a coil and a magnet? A. by placing the coil parallel to the magnetic field B. by placing the coil at right angles with the magnetic field C. by moving either the magnet or the coil D. by keeping the coil and the magnet perfectly stationary

C

If X is low, what is the state of X AND Y? A. not enough information to tell B. high C. low D. this logic makes no sense

C

If a certain circuit has a current that is lagging the voltage by 45deg, then it displays A. pure inductive reactance B. resistance and capacitive reactance C. resistance and inductive reactane D. pure capacitive reactance

C

In a P-channel JFET: A. the drain is forward-biased B. the gate-source junction is forward biased C. the drain is negative relative to the source D. the gate must be at the dc ground

C

In the circuit below, the Zener diode has a breakdown voltage Vzt=8.0V and a measurement has shown that Vz=8.6V when Iz=30mA. What is the value of Vout when Rl becomes infinitely large? A. 0V B. 8.2V C. 8.8V D. 8.4V

C

It can also be used to locate the source of a field, and to measure the performance of radio frequency shielding. A. oscilloscope B. logic analyzer C. RF meter D. spectrum analyzer

C

Selenium works especially well in A. high-frequency detectors B. radio-frequency power amplifiers C. photocells D. voltage regulators

C

Suppose that an ion source in a mass spectrometer produces doubly ionized gold ions each with a mass of 3.27x10^-25 kg. The ions are accelerated from rest rhrough a potential difference of 1.00kV. Then, a 0.500-T magnetic field causes the ions to follow a circular path. Determine the radius of the path. A. 8.0 cm B. 8.5 cm C. 9.0 cm D. 9.5 cm

C

The distance between the capacitor plates increases two times, then its capacitance A. increases two times B. increases four times C. decreases two times D. decreases four times

C

The magnetic flux through a wire loop in a magnetic field does not depend on the___. A. area of the loop B. magnitude of the field C. shape of the loop D. angle between the plane of the loop and the direction

C

The maximum voltage output from a voltage divider: A. is a fraction of the power supply B. depends on the total resistance C. is equal to the supply voltage D.depends on the ratio of the reistances

C

The period of an ac wave is A. the same as the frequency B. not related to the frequency C. equal to 1 divided by the frequency D. equal to the amplitude divided by the frequency

C

The permeability of permalloy is A. slightly less than permeability of air B. slightly greater than permeability of air C. very much larger than permeability of air D. equal to the permeability of air

C

To turn off the SCR, which of the following is done? A. reduce gate voltage to zero B. reverse bias the gate C. reduce anode voltage to zero D. deuce cathode voltage to zero

C

What current is required in the windings of a long solenoid that has 1000 turns uniformly distributed over a length of 0.40m in order to produce a magnetic field of magnitude 1x10^-4 T at the center of the solenoid A. 29.8mA B. 31.3mA C. 31.8mA D. 32.3mA

C

A __ is like two parallel SCRs having a common gate and connected opposite directions A. UJTs B. PUTs C. Diacs D. Triacs

D

A changing magnetic field A. results from a steady electric current B. magnetizing the earth C. produce an electric current in the insulator D. produce a fluctuation electric field

D

A coil is represented by a series combination of L=50mH and R=15ohms. Calculate the quality factor at 10khz. A. 1047 B. 845 C. 326 D. 209

D

A current surge take place when a power supply is turned on because A. the transformer core is suddenly magnetize B. the diode suddenly start to conduct C. the filter capacitor must be initially charged D. arcing takes place in the power switch

D

A theorem which states than an electric current flowing in a circuit produces a magnetic field at external points equivalent to that due to a magnetic shell whose bounding edge is the conductor and whose strength is equal to the strength of the current. A. joules' law B. faraday's law C. volta's theorem D. ampere's theorem

D

Calculate the total harmonic distortion for the amplitude components given D2=0.10, D3=0.04 and D4=0.02 A. 115 B. 10.75% C. 11.95% D. 10.95%

D

How can a class amplifier be made linear? A. by reducing the bias B. by increases the drive C. by adding two transistor in push-pull D. a class-C amplifier cannot be made linear

D

Hysteresis refers to the ___ between flux density of the material and the magnetizing force applied. A. leading effect B. ratio C. equality D. lagging effect

D

Hysteresis refers to the ___ between flux density of the material and the magnetizing force applied. A. ratio B. equality C. leading effect D. lagging effect

D

In a RAM: A. it's easy to get data out and hard to put it in B. it's hard to get data out and easy to put it in C. it's hard to get data out and put it in D. it's easy to get data out and put it in

D

In small inductance: A. energy is stored and release slowly B. the current flow is always large C. the current flow is always small D. energy is stored and release quickly

D

Power absorbed in a pure capacitive circuit is zero because A. reactive and active components of the current cancel out B. reactive component of the current is zero C. active component of the current is maximum D. power factor of the circuit is zero

D

The gigabyte is a unit commonly used to measure of A. data access time B. data transfer time C. data communication accuracy D. data storage capacity

D

The input impedance of a MOSFET: A. is lower than the JFET B. is lower than the bipolar transistor C. is between that of the bipolar transistor and a JFET D. is extremely high

D

The number of protons in the nucleus of an element is the: A. electron number B. valence number C. proton number D. atomic number

D

The principal disadvantage of a voltage multiplier is A. excessive current B. excessive voltage C. insufficient rectification D. poor regulation

D

To measure power-supply voltage being used by a circuit, a voltmeter A. is placed in series with the circuit that works from the supply B. is place between the positive pole of the supply and the circuit working from the supply C. is place between the negative pole of the supply and the circuit working from the supply D. is place in parallel with the circuit that works from the supply

D

What is the minimum fan-out of TTL? A. 5 B. 20 C. 10 D. 2

D

What maximum power can a silicon transistor (Tjmax= 200degC) dissipate into free air at an ambient temperature of 80degC? A. 0.5W B. 1W C. 2W D. 3W

D

When phase shifting an SCR, what two things must be phase shifted? A. variable resistor and gate current B. variable resistor and capacitor C. variable inductor and gate current D. variable capacitance and gate current

D

Which of the following voltmeter has the most inaccurate reading? A. low sensitive, 900 micro ohms B. low sensitive, 90 milli ohms C. low sensitive, 90 micro ohms D. low sensitive, 900 k ohms

D

Why is it that the magnitude of magnetomotive force required for air gap is much greater than that required from iron part of a magnetic circuit? A. because air is a gas B. because air has the highest relative permeability C. because air is a conductor of magnetic flux D. because air has the lowest relative permeability

D