BASIC PRINCIPLES - Day 1

Question 1: EE Board October 1998
     The resistance of 120 meters of wire is 12 ohms. What is its conductance?

A. 12 mhos
B. 6 mhos
C. 0.083 mho
D. 0.0521 mho


Question 2: EE Board October 1992
     The insulation resistance of a kilometer of the cable having a diameter of 2 cm and an insulation thickness of 2 cm is 600 ohms. If the thickness of the insulation is increased to 3 cm, find the insulation resistance of the cable.

A. 828 ohms
B. 757 ohms
C. 850 ohms
D. 725 ohms




Question 3:
     The diameter of a given bare conductor is 0.50 inch. A thermoplastic insulation with thickness of 0.1 inch is wrapped around to insulate the conductor. Determine the insulation resistance of this conductor per meter. Assume specific resistance of thermoplastic insulation to be 2 x 10^14 ohm-cm.


A. 109 x 10^9 Ω
B. 110 x 10^9 Ω
C. 105 x 10^9 Ω
D. 107 x 10^9 Ω     



Question 4:
     A cylindrical rubber insulated cable has a diameter of 0.18 inch and an insulation of thickness of 0.25 inch. If the specific resistance of rubber is 10^14 ohm-cm, determine the insulation resistance of 1000-ft lenght of the cable.

A. 694 MΩ
B. 678 MΩ
C. 682 MΩ
D. 624 MΩ




Question 5: EE Board October 1991
     Two heating element which is 500 ohms and 250 ohms are connected in series with temperature coefficients of 0.001 and 0.003 ohms per ⁰C, respectively at 20 ⁰C. Calculate the effective temperature coefficient of the combination.

A. 0.00167
B. 0.00712
C. 0.00626
D. 0.00215


Question 6:
     Two wires A & B made from two different materials have temperature coefficient of resistance equal to 0.0025 and 0.0005 ohm per ⁰C, respectively. It is desired to make a coil of wire having a resistance of 1200 ohms with a temperature coefficient of 0.001, using the suitable length of the two given wires connected in series. Determine the required length of wire.

A. 5.0 m
B. 6.0 m
C. 6.2 m
D. 5.5 m


Question 7: EE Board March 1998
     The resistance of a wire is 126.48 ohms at 100 ⁰C and 100 ohms at 30 ⁰C. Determine the temperature coefficient of copper at 0 ⁰C.

A. 0.0356
B. 0.0256
C. 0.00615
D.  0.00427




Question 8:
     The field winding of a series motor has a resistance of 120 ohms at 15 ⁰C. After running for two hours, the resistance increases to 140 ohms. If the temperature coefficient of the windings at 0⁰C is 0.004, find the new temperature of the windings.

A. 53.7 ⁰C
B. 58.4 ⁰C
C. 59.2 ⁰C
D. 60.4 ⁰C

Question 9:
     The shunt field winding of a shunt generator has a resistance of 80 ohms at 20⁰C. After several hours of continuous operation, the winding temperature rises to 50⁰C. How much is the winding resistance under this condition. Assume the resistance temperature coefficient of copper to be 0.004 ohm per degree at 0⁰C.

A. 92.81 ohms
B. 85.22 ohms
C. 90.12 ohms
D. 88.89 ohms




Question 10:
     The resistance of a copper wire at 30⁰C is 50 ohms. If the temperature coefficient of copper at 0⁰C is 0.00427, what is the resistance at 100⁰C?

A. 58.15 ohms
B. 63.24 ohms
C. 54.25 ohms
D. 72.26 ohms