chitika 1

Tuesday, April 19, 2011

BASIC PRINCIPLES - Day 3

Question 1:
    A positively charged dielectric has a charge of 2 coulombs. If 12.5 x 1018 free electrons are added to it, what will be the net charge on the said dielectric?
A. 4 C
B. -2 C
C. 8 C
D. Zero


Question 2:
    A battery can deliver 10 joules of energy to move 5 coulombs of charge. What is the potential difference between the terminals of the battery?
A. 2 V
B. 50 V
C. 0.5 V
D. 5 V


Question 3:
     A cloud of 2.5 x 1019 electrons move past a given point every 2 seconds. How much is the intensity of the electron flow?
A. 1 A
B. 2 A
C. 2.5 A
D. 1.5 A


Question 4:
     The current in an electric lamp is 5 amperes. What quantity of electricity flows towards the filament in 6 minutes?
A. 30 C
B. 3600 C
C. 72 C
D. 1800 C


Question 5:
     A constant current of 4 A charges a capacitor. How long will it take to accumulate a total charge of 8 coulombs on the plates?
A. 2 s
B. 32 s
C. ½ s
D. 12 s


Question 6: EE Board March 1998
     The substation bus bar is made up of 2-iches 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 ohm
B. 13.8 x 10-6 ohm
C. 5.185 x 10-5 ohm
D. 2.96 x 10-5 ohm


Question 7: EE Board October 1997
     Determine the resistance of a bus bar 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 ohm
B. 4.312 x 10-4 ohm
C. 3.431 x 10-5 ohm
D. 1.078 x 10-4 ohm

Question 8:
     Nichrome ribbon resistor elements each has a resistance of 1 ohm. The element is made from sheet of nichrome alloy, 0.025 cm thick. If the width of the ribbon is 0.3 cm, what length is required per element? Assume specific resistance of nichrme alloy to be 109 µΩ-cm.
A. 68.8 cm
B. 62.1 cm
C. 70.7 cm
D. 67.4 cm

Question 9: EE Board October 1991
     One turn of a copper bar is produced by cutting a copper washer along a radius and spreading the ends. The washer is cut from soft-drawn copper having a resistivity at 200C 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 ohm
B. 15.53 x 10-6 ohm
C. 17.22 x 10-6 ohm
D. 14.83 x 10-6 ohm
  

Question 10: EE Board 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 one end of the conductor according to the formula: ρ = 0.003 + 10-4 L2 ohm-cm.
A. 0.0852 ohm
B. 0.0915 ohm
C. 0.0806 ohm
D. 0.0902 ohm

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