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DC CIRCUITS > PART 1 > Flashcards

PART 1 Flashcards

1
Q
  1. REE Board Exam March 1998

The substation bus bar is made up of 2 inches round copper bars 20 ft. long. What is the resistance of each bar if resistivity is 1.724 x 10-6 ohm-cm.

A. 7.21 x 10-5 Ω

B. 13.8 x 10-6 Ω

C. 5.185 x 10-5 Ω

D. 2.96 x 10-5 Ω

A

A

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2
Q
  1. REE October 1997

Determine the resistance of a busbar made of copper if the length is 10 meters long and the cross section is a 4 x 4 cm2. Use 1.7241 micro ohm-cm as the resistivity.

A. 2.121 x 10-4 Ω

B. 4.312 x 10-4 Ω

C. 3.431 x 10-5 Ω

D. 1.078 x 10-4 Ω

A

D

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3
Q

EE Board Exam October 1991

One turn of a copper bar is produced by cutting copper washer along a radius and spreading the ends. The washer is cut from soft drawn copper having a resistivity at 20°C of 1.732 x 10-6 ohm-cm. The washer is 0.125 inch thick and has inside diameter and outside diameter of 1 inch and 9 inches respectively. Calculate the exact resistance between the two ends of the turn to direct current, taking into account the non-uniform current distribution. Assume the contact along the ends of the turn to be perfect over the entire cross section.

A. 12.74 x 10-6 Ω

B. 15.53 x 10-6 Ω

C. 17.22 x 10-6 Ω

D. 14.83 x 10-6 Ω

A

B

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4
Q

EE Board Exam October 1990

Determine the resistance of a conductor 0.10 m long, with a uniform diameter of 1.0 cm and having a resistivity which varies as a function of length L measured from the one end of the conductor according to ρ = 0.003 + 10-4 L2 ohm-cm.

A. 0.0852 ohm

B. 0.0915 ohm

C. 0.0806 ohm

D. 0.0902 ohm

A

C

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5
Q

EE Board Exam April 1992

A coil has 6,000 turns of wire and a resistance of 380 ohms. The coil is rewound with the same quantity (weight) of wire, but has 13,400 turns. How many ohms will the new coil have?

A. 1895 ohms

B. 1825 ohms

C. 1792 ohms

D. 1905 ohms

A

A

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6
Q

EE Board Exam April 1992

A copper wire of unknown length has a resistance of 0.80 ohm. By successive passes through drawing dies, the length of the wire is increased by 2 ½ times its original value. Assuming that resistivity remains unchanged during the drawing process, determine the new value of its resistance.

A. 4 ohms

B. 3 ohms

C. 5 ohms

D. 6 ohms

A

C

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7
Q

REE Board Exam October 1998

A one-meter rod of 2-cm diameter is drawn until its resistance is 100 times the initial resistance. Its length afterwards is?

A. 10 m

B. 100 m

C. 12.5 m

D. 5 m

A

A

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8
Q

EE Board Exam April 1993

A kilometer of wire having a diameter of 11.7 mm and a resistance of 0.031 ohm is drawn down so that its diameter is 5.0 mm. What does its resistance become?

A. 0.85 ohm

B. 0.78 ohm

C. 0.93 ohm

D. 0.81 ohm

A

C

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9
Q

EE Board Exam April 1995

A certain wire has a resistance R. The resistance of another wire identical with the first except for having twice its diameter is

A. 4R

B. R/2

C. 2R

D. R/4

A

D

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10
Q

REE Board Exam October 1996

What is the size in square millimeter (mm2) is the cable of 250 MCM size?

A. 118.656 mm2

B. 126.675 mm2

C. 112.565 mm2

D. 132.348 mm2

A

B

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11
Q

REE Board Exam October 1998, September 2001

The resistance of a copper wire at 30°C is 50 ohms. If the temperature coefficient of copper at 0°C is 0.00427, what is the resistance at 100°C?

A. 72.26 ohms

B. 54.25 ohms

C. 63.24 ohms

D. 58.15 ohms

A

C

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12
Q

REE Board Exam March 1998

The resistance of a wire is 126.48 Ω at 100°C and 100 Ω at 30°C. Determine the temperature coefficient of copper at 0°C.

A. 0.00427/°C

B. 0.00615/°C

C. 0.0256/°C

D. 0.365/°C

A

A

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13
Q

EE Board Exam April 1989

It is required that a loading of 3 kW be maintained in a heating element at an initial temperature of 20°C, a voltage of 220 V is necessary for the purpose. After the element has settled down to steady state, it is found that a voltage of 240 volts is necessary to maintain the 3 kW loading. The element resistance temperature coefficient is 0.0006 per degree centigrade at 20°C. Calculate the final temperature of the heating element.

A. 345.43°C

B. 326.42°C

C. 336.84°C

D. 318.48°C

A

C

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14
Q

REE Board Exam October 1999

How long must a current of 5 A pass through a 10 ohm resistor until a charge of 12000 coulomb passes through?

A. 1 min

B. 2 min

C. 3 min

D. 4 min

A

D

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15
Q

REE Board Exam October 1999

What is the power required to transfer 97,000 coulombs of charge through a potential rise of 50 volts in one hour?

A. 0.5 kW

B. 0.9 kW

C. 1.3 kW

D. 2.8 kW

A

C

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16
Q

REE Board Exam April 2001

A round wire has 250 MCM. Find its diameter in inches.

A. ½

B. ¼

C. 0.16

D. 0.08

A

A

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17
Q

REE Board Exam September 2003

In the American wire gauge, as the number of gauge increases, the diameter of wire _____

A. increases

B. decreases

C. does not change

D. become twice

A

B

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18
Q

REE Board Exam September 2003

In cgs system, what is the unit of emf where I is in abampere and P is in erg per second?

A. millivolt

B. kilovolt D

C. abvolt

. volt

A

C

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19
Q

REE Board Exam September 2002

One (1) kW is equal to ____ hp.

A. 0.746

B. 1.34

C. 550

D. 1.5

A

B

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20
Q

REE Board Exam October 1998

Two copper conductors have equal length. The cross-sectional area of one conductor is three times that of the other. If the resistance of the conductor having smaller cross-sectional area is 20 Ω, what is the resistance of the other?

A. 20/3 Ω

B. 60 Ω

C. 180 Ω

D. 20/9 Ω

A

A

21
Q

REE Board Exam October 2000

A copper bar has a length of 20 ft., width of 4 inches and thickness of 0.5 inch. If the resistivity of copper is 10.37 Ω-CM/ft, what is the resistance of the bar?

A. 81.4 μΩ

B. 8.14 μΩ

C. 814 μΩ

D. 0.814 μΩ

A

A

22
Q

REE Board Exam April 2001

The resistance of the field winding of a DC machine is 0.25 Ω at 25°C. When operating at full-load, the temperature of the winding is 75°C. The temperature coefficient of resistance of copper is 0.00427 per °C at 0°C. Find the resistance of the field winding at full-load.

A. 0.298 Ω

B. 0.315 Ω

C. 0.512 Ω

D. 0.271 Ω

A

A

23
Q

REE Board Exam October 2000

A coil of copper has resistance of 5.46 Ω at 75°C. What will be its resistance at 25°C?

A. 4.58 Ω

B. 4.84 Ω

C. 5.02 Ω

D. 4.35 Ω

A

A

24
Q

REE Board Exam April 2001

A certain generator generates 1,500,000 joules per minute. What is the output in kW?

A. 50

B. 500

C. 25

D. 125

A

C

25
Q

ECE BOARD NOV 2001

_____ is anything that has weight had occupies space. It may be solid, liquid or gas.

A. Amalgam

B. Alloy

C. Matter

D. Compound

A

C

26
Q

ECE Board Exam April 2000

It is defined as anything that occupies space and has weight.

A. atom

B. compound

C. molecule

D. matter

A

D

27
Q

ECE Board Exam November 1999

The lightest kind of atom or element

A. hydrogen

B. helium

C. titanium

D. oxygen

A

A

28
Q

ECE Board Exam November 1998

In order to have a good conductor material, such material shall have _____ valence electrons.

A. one

B. five

C. more than ten

D. twenty one

A

A

29
Q

ECE Board Exam November 1997

Electric power refers to _____

A. volt ampere

B. watt second

C. volt coulomb

D. joule

A

A

30
Q

ECE Board Exam November 1995

What composes all matter whether a liquid, solid or gas?

A. electrons

B. atoms

C. protons

D. neutrons

A

B

31
Q

ECE Board Exam November 2001

What is a physical combination of compounds or elements NOT chemically combined that can be separated by physical means?

A. substance

B. atom

C. mixture

D. molecule

A

C

32
Q

ECE Board Exam April 1998

Determine the equivalent work of 166 watt-second.

A. 10 joules

B. 100 joules

C. 16.6 joules

D. 166 joules

A

B

33
Q

ECE Board Exam November 2001

One of the following is the best conductor of electricity.

A. Air

B. Copper

C. Carbon

D. Silicon

A

B

34
Q

ECE Board Exam November 1999

What is the basic unit for measuring current flow?

A. coulomb

B. ampere

C. volt

D. atomic weight

A

B

35
Q

ECE Board Exam November 1995

______ has a unit of electron volt

A. Energy

B. Potential difference

C. Current

D. Charge

A

A

36
Q

ECE Board Exam November 2001

The motion of charged particles especially colloidal particles through a relative stationary liquid under the influence of an applied electric provided.

A. hysteresis

B. electrolysis

C. electrophoresis

D. electro analysis

A

C

37
Q

ECE Board Exam April 2001

What is a symbol that represents a quantity or a single object?

A. unit

B. number

C. item

D. base

A

A

38
Q

ECE Board Exam April 2000

Determine which of the following has the least number of electrons found at the outer shell.

A. semi-insulator

B. insulator

C. semiconductor

D. conductor

A

D

39
Q

ECE Board Exam April 2001

The term describes a material whose resistance remains relatively constant with changes in temperature

A. positive temperature coefficient

B. negative temperature coefficient

C. neutral temperature coefficient

D. zero temperature coefficient

A

D

40
Q

ECE Board Exam November 1998

Resulting effect when electron is made to move

A. dynamic electricity

B. static electricity

C. lines of force

D. magnetic lines

A

A

41
Q

ECE Board Exam November 1997

One of the following characteristics of a resistive material which do not change its resistive value with respect to time is its _____

A. fidelity

B. sensitivity

C. stability

D. selectivity

A

C

42
Q

ECE Board Exam November 2001

What do you call the element that conducts electricity very readily?

A. semi-conductors

B. conductors

C. insulators

D. dielectric

A

B

43
Q

ECE Board Exam April 2001

Which of the following material is referred to as a medium whereby electrons can move easily from atom to atom?

A. insulator

B. dielectric

C. mica

D. conductor

A

D

44
Q

ECE Board Exam November 2001

A chemical combination of elements can be separated by chemical means but not by physical means. It is created by chemically combining two or more elements.

A. molecules

B. compound

C. matter

D. mixture

A

B

45
Q

ECE Board Exam April 2000

A substance which cannot be reduced to a simpler substance by chemical means

A. atom

B. molecule

C. matter

D. element

A

D

46
Q

ECE Board Exam November 2001

Calculate the equivalent power in watt of 100 joules per second.

A. 1.66 watts

B. 100 watts

C. 16.66 watts

D. 1,000 watts

A

B

47
Q

ECE Board Exam April 2001

It is a neutral particle that has no electrical charge.

A. atom

B. proton

C. electron

D. neutron

A

D

48
Q

ECE Board Exam November 1999

Which material has more free electrons?

A. mica

B. insulator

C. conductor

D. dielectric

A

C

DC CIRCUITS (2 decks)

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