BASIC PRINCIPLES - Day 2

Question 1: EE Board 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

Question 2: EE Board 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 to 2 ½ times its original value. Assuming that resistivity remains unchanged during the drawing process, determine the new value of its resistance.

A. 4 Ω

B. 3 Ω

C. 5 Ω

D. 6 Ω

Question 3: EE Board October 1998

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

A. 10 m

B. 100 m

C. 12.5 M

D. 5 m

Question 4: EE Board 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

Question 5:

     A conductor whose diameter is 0.175 inch has a resistance of 0.5 ohm. The wire is drawn through a series of dies until its diameter is reduced to 0.08 inch. Assuming the specific resistance of the material remains constant, what is the resistance of lengthened conductor?

A. 11.45 Ω

B. 10.22 Ω

C. 12.75 Ω

D. 10.82 Ω

Question 6: EE Board 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. ½R

C. 2R

D. ¼ R

Question 7:

     A given wire has a resistance of 17.5 ohms. If its length is 560 m, how much length must be cut-off from the wire in order to reduce its resistance to 12.5 ohms.

A. 160 m

B. 170 m

C. 145 m

D. 155 m

Question 8: EE Board 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

Question 9:

     A 500 MCM ACSR cable has 37 strands. Determine the diameter in mils of each strand.

A. 116.25

B. 120.24

C. 118.34

D. 110.35

Question 10:

     A copper transmission line is to be replaced by one of aluminum having the same total resistance. If the cross sectional area of the copper wire is 500 MCM, what would be the cross sectional area of the new aluminum wire?

A. 800 MCM

B. 820 MCM

C. 850 MCM

D. 900 MCM