EE MODULE 2

100問 • 1年前

問題一覧

A coil of wire having a value of 10+ j 16 ohms is connected in series with a capacitance reactance Xc, and this series combination is then connected in parallel with resistor R. if the equivalent impedance of the circuit is 8 + 100, what is the value of Xc in ohms ?

A transponder with a bandwidth of 400 MHz uses polarization diversity. If the wavelength allocated to transmit a single telephone channel is 4 kHz, how many telephone channels can be carried by the transponder?

100,000

A room air conditioner is to be attached to an individual branch circuit. If the load is 12 A, what is the minimum size of branch circuit required?

15 A

Which of the following type of fault that used only the equivalent positive impedance of the circuit in the short-circuit calculation?

Three phase fault

A washing machine is, in effect, an R-L circuit. If the machine takes 311 W and 4.5 A from a 155-V source when operating normally. Find its power factor.

0.60 lagging

Which of the following define the meaning of load factor?

The ratio of average load to maximum load.

If the magnetic flux through a certain region is changing with time

an emf exist around the boundary

In a capacitor start motor, the capacitor is replaced by an inductor having the same reactance as in capacitor. Then the motor will

not start

Which of the following AC device is used to measure the angle between the voltage and its current?

phase angle meter

A flux of 13.6 mWb penetrates a coil of wire 240 mm in diameter. Find the magnitude of the magnetic flux density in Tesla if the plane of the coil is perpendicular to the field.

0.3

A single-phase inductive load draws 10 MW at 60% lagging power factor. Determine the reactive power of the capacitor in MVAR to be connected in parallel with the load to raise the power factor to 85%

A resistor with resistance R1 and a resistor with resistance R2 are connected in parallel to an ideal battery with emf V. What is the rate of thermal energy generation in the resistor with resistance R1?

V2/R1

The grounded conductor is a/an _______ grounded conductor

intentionally

The resistance of a rod does NOT depend on

The shape of its cross sectionla area

When the amplitude of the oscillator in a series RLC circuit is doubled the

current amplitude is doubled

Which of the following protective device operates on the principle of Kirchoff's Current Law?

Differential Protective Relay

Which of the following will the effect of the electric shock in the human body depend on?

current flowing in the body

The coulomb force F, acts on two charges a distance, r, apart. What is F proportional to?

1/r^2

An LC series circuit with an inductance L and a capacitor C has an oscillation frequency of f. Two inductors, each with inductance L, and two capacitors, each with capacitance C, are all wired in series and the circuit is completed. The oscillation frequency is

f/2

Which of these is NOT a simplex type of electronic communication?

Telephone

A good example of kinetic energy is provided by

a tornado

A 60 Hz alternator has a speed of 300 rpm. How many poles has it?

Current has units of

coulomb/second

A stationary conducting loop with an internal resistance of 0.50 ohm is placed in time- varying magnetic field. When the loop is closed, a current of 5 A flows through it. What will the current be if the loop is opened to create a small gap and a 2-ohm resistor is connected across its open ends?

1 A

The readings of the wattmeter will be the same in two-wattmeter method when

power factor is unity

Modern locomotives are powered by DC motors driven by DC generators. Those are, in turn, driven by diesel engines. Which of the following is the reason for using such a configuration instead of AC general-motor sets?

The DC configuration provides high torque and good incremental power at low speeds, and performs equally well at high speeds

What is the main reason that alternating current replaced direct current for general used?

AC voltages conveniently transformed.

What can usually be assumed as the driving or source voltage for fault and voltage calculations in per unit method?

1 p.u

Which of the following is NOT a reason why single-phase induction motor run?

Two windings displaced from each other

Which of the following is normally a controlled grounding path for current flow?

high impedance circuit

Two millions cu, m. of water is stored in a reservoir feeding water turbine. If the center of the mass is 50m above the turbine and losses are negligible. The density of the water is 993 kg/cu.m. How much energy in MWh/s will that volume of water produce?

271

A series circuit consists of a 20 Ω resistor, a 0.20 H inductor, and 50 microfarad capacitor. If a variable frequency 120 V source is connected across its terminal, what is the resonant frequency in Hz?

In a single-phase transformer, the core losses is 60 W at 40 Hz and 95 W at 60 Hz both measured at the same maximum value of the flux density. Find the core losses in W at the frequency of 50 Hz.

A uniform magnetic field makes an angle of 30° with the z axis. If the magnetic flux through a 1-m² portion of the xy plane is 5 Wb then the magnetic flux through a 2-m² of the same plane is ______ Wb.

A symmetrical three-phase 240 V supplies a balanced delta-connected load of 6-18 ohms per phase. What is the line current?

25 + j32 A

The hazards exist only during the period of the time the ________ is there

fault

A 60-Hz induction motor has two poles and runs at 3510 rpm. of the What is the synchronous speed of the induction motor

3600 rpm

At a certain location in Australia, it is necessary to supply 300 kW of 60 Hz power. The only power sources available operate at 50 Hz. It is decided to generate the power by means of a motor-generator set consisting of a synchronous generator. How many poles should each of the two machines in order to convert 50 Hz to 60 Hz power? A 10 pole motor supplied at 50Hz runs at 600 rpm. The generator driven at 600rpm, the generated frequency is

A 10-pole synchronous motor coupled to a 12-pole synchronous generator

The resistance of resistor 1 is twice of resistor 2. The two are connected in SERIES and a potential difference is maintained across the combination. What is the rate of thermal energy generation in resistor 1?

Twice that in resistor 2

A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its charge is half the final value. What is the time constant on this process in ms?

What is the function of the surge tank in the hydro power plant?

Relieve water hammer pressures in the penstock pipe

Which of the following is NOT a property of magnetic field lines?

Magnetic field lines have no beginning and no ends.

What is the maximum speed at which a 60Hz synchronous machine can be operated?

3600 rpm

Is the ground can be intentional or accidental? I. True II. Flase

I only

In the oscillating LC circuit, then total stored energy is U. the maximum energy stored in the capacitor during one cycle is

U/2

What is the function of protective relays in the protection scheme?

sensing device

Three single-phase transformers rated 25 kVA each are connected in delta-delta to supply a balanced load of 75 kVA. One transformer is removed for repair, what is the KVA of each remaining transformer?

43.3

A power plant consumes 3,000 tons of coal per day. The coal has an average energy content of 10,000 BTU/lb. the power plant has an overall efficiency of 25%. what is the plant power output in MW?

183

What is the electrical analog of a spring constant "k"?

The starting/ in rush current of the transformer is generally __________ times of its full load current

Find the power factor of a circuit that absorbs 1.5 kW for 230-V Input voltage and a 8-A current.

0.815

A symmetrical positive sequence four bus Z11 =j 0.27, Z12= j 0.24, Z13=0.17, Z 14=j 0.20,Z22=j 0.29 723 =i0.20,Z24=;0.24 = j 3.0, Z34= j 0.26, and Z44 = j 0.38, all in p.u. what is the three-phase fault at Bus 3?

- j 3.33 p.u

The current in a coil decreases from 30 A to 10 A in 0.2 sec. If the self-inductance of the coil is 4 H, what is the induced emf in V?

400

The rotor of a three-phase, 60 Hz, 4-pole inductor motor takes 120 kW at 3 Hz. What is the rotor speed of the induction motor?

1710 rpm

A transformer takes 5.175 kW at a power factor of 0.85 when connected to a 2.3 kV distribution circuit. What is the current input in Amp.?

2.65

If lVsl = lVrl = 33 kV (three phase) and x =13 ohm per phase, what will be the maximum power transmission per phase?

28 MW

Which of the following transformer's winding connection is load?

Four-wye

Which of the following instrument is suited for high frequency?

Thermocouple

What is the actual voltage of the high-temidales to the three-phase, four-wire delta grounded system 240/120 V secondary voltage?

208 V

Positive charge is distributed uniformly throughout a non-conducting sphere. The highest electric potential occurs

at the surface

Two wires of the same material have the same length but different diameters. They are connected in SERIES to a battery. Which of the following quantity is the same for the two wires

Current

The Tesla is a unit of

magnetic flux density

Which of the following limits the number of coils that may be placed on the armature of a DC motor or generator?

the type of winding used

The per phase line loss in a 40 km long transmission line is NOT to exceed 60 kW while it is delivering 100 A per phase. If the resistivity of the conductor material is 1.72 x 10-8 ohm- meter, determine the required conductor diameter

1,2083 cm

What is the allowable rating for branch overload protection if fuse is used for the hermetic motor compressor with a rated load current of 37 A?

30 A

Two 110-V light bulbs, one "25 and the other "100 W" are connected in series to a 110 V source. Then, which of the following statement is correct with regard to above sentence?

For series circuit with different values of Resistance, current is constant and voltages Intellectual Property of across are different

A parallel plate capacitor with plates of area A that are separated a distance d by air is initially charged with charge q. The energy stored in the capacitor initially is

A coil of wire having a resistance of 3.75 ohm and carrying a current of 0.3 A is in parallel with an unknown resistance through which there a current of 1.5 A. Determine the total equivalent resistance.

0.625 ohm

The primary of a transformer has 200 turns and is excited by a 60 Hz, 200 V source. What is the maximum value of the core flux

4.13 mWb

A source with an impedance of 100 2 is connected to the primary coil of a transformer and a resistance R is connected to the secondary coil. If the transformer has 100 turns in the primary coil and 100 turns in the secondary coil the greatest power will be dissipated in the resistor if R= ______ ohm

100

The magnetic torque exerted on a flat current-carrying loop of wire by a uniform magnetic field B is

maximum when the plane of the loop is perpendicular to B.

Two resistors are connected in parallel across a potential difference. The resistance of resistor A is twice that of resistor B. If the current carried by resistor a is I, then the current carried by B?

The growth rate of the energy consumption in our country is 6.9%. In how many years will the energy be quadrupled?

A wind generator with an efficiency of 80% has blase diameter of 20 m

54.78

Which of the following is/are the MOST important factor/s to be considered in the selection of fuel for power plants? I. Cost of fuel II. Calorific value fuel

Both I and II

What is ACSR conductor stands for?

Aluminum Cable Steel Reinforced

A certain galvanometer has resistance of 100 Ω and requires 1 mA for full scale deflection. To make this into a voltmeter reading of 1 full scale. Connect a resistance of

900 ohms in series

If the appliance has a motor load of 12 - A and a heating load of 15-A, what is the required ampacity of the branch circuit conductors?

30 A

The government agency created under Presidential Degree 269, whose additional mandates includes preparing electrical cooperatives in operating and competing under a deregulated electricity market.

National Electrification Administration

Α 3 0 ohms and 1.51 ohms resistors are wired in parallel and the combination is wired in SERIES to a 4 resistor and a 10-V emf device. What is the current in the 30 resistor?

0.67 A

Two compound generators are connected in parallel. If generator A has a series-field resistance of 0.0015 ohm and is adjusted to take 30% of the line load while generator B with a series field resistance of 0.001 ohm takes the remainder of the load. Determine the current flow in the equalizer when the load is 230kW at 230V

100A

What is the maximum output of cellular transmitter?

The voltage regulation is an important factor in the design of

Feeder

What is/are the main reason/s for using high voltage in the transmission of power in grid systems? I. To transmit bulk power with minimum losses II. To increase system reliability

I only

AC system has the following disadvantages over DC system

Charging current level

What is the minimum branch circuit/ampacity of supply feeder for a window type air conditioning unit with 8-A rated load current with other load supplied?

When one coil of magnetically coupled pair has a current of 5 amperes, the resulting flux Phi_{11} = 0.4mWb and flux Phi_{12} = 0.8 mWb respectively. If the turns are N_{1} = 500 and N_{2} = 1500 . Find the L2.

1080 mH

In two winding unloaded transformer, the flux linking the primary and secondary winding are 10mWb and 8 mVWb respectively. What is the coupling coefficient

0.9

Three impedances, Z1=6cis 20deg, Z2=8cis 40deg and Z 3=10+i0 ohms are connected in wye and supplied by a 480 volts three phase source. What is the equivalent delta connected impedance at phase 17

14.17 + j11.35

Increasing the power output of alternator working in parallel to a large system, the operator must adjust

Governor

Referring to the sending end voltage, what is the value of receiving end voltage at no load for medium transmission lines? I. higher II. Lesser III. Remains constant

I only

Where does a fluorescent lamp cannot be mounted that easily causes fire?

cellulose fiber

What is the PEC rule for the sizing wire and protection?

Wiring Design Rule

The process of modifying high frequency carrier with the information to be transmitted is called

Modulatio

Single phase transformer is rated 100kva, 20000/230 volts has an equivalent impedance referred to the primary of 60 ohms. What is the percent impedance of the transformer.?

1.5

What is the frequency used in communication such as mobile phones?

UHF

A four pole generator has 500 conductors on the armature. If the generator is running at 1000 rpm, find the average voltage generated between brushes for wave winding. The total flux per pole is 1.2x105 lines.

200 V

Two 60 ohms resistance are connected in series across 120 volt de source. Find the value of resistor R in ohms to be connected across one of the two 60 ohms resistors so that the total resistance is 90 ohms

Who is not been a member of the Board of Electrical Engineering?

Renato Cayetano

100

A 1.5 kW single phase converter operates at full load from a 230 volt a-c source. Neglecting the losses and assuming a power factor of unity calculate the de output voltage.

325.3 V

DC CIRCUITS POWERLINE

premopremo remo · 75問 · 2年前

DC CIRCUITS POWERLINE