# Electrical Quantities & Units

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 Author: cxcxcx ID: 221074 Filename: Electrical Quantities & Units Updated: 2013-05-25 11:43:13 Tags: Electrical Quantities Units Pocket Folders: Description: Electrical Quantities & Units Show Answers:

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1. Determine the maximum number of electrons that can exist in the third shell of an atom?
• ,
2. Determine the magnitude of the voltage required to accelerate an electrons to a kinetic energy of 8 x 10^-15 joules?
3. A car battery supplies a current of 50 A to the starter motor. How much charge passes through the starter in 1/2 minute?
4. How many circular mils does a round copper rod of 0.25 inch diameter has?
5. What is the size in square millimeter is the cable of 250 MCM size?
• 250 MCM → 250000 CM

6. A copper rod of 10m long has a diameter with one inch. If the resistivity of copper is 10.371 ohms circular-mil per foot, what is the resistance?
7. Determine the resistance of a bus bar of copper if the length is 10 meters long and the cross section is a 4 x 4 cm. The resistivity is 1.724μohm-cm.

• R
8. A one meter rod of 2cm diameter is drawn until its resistance is 100 times the initial resistance. its length afterward is?
9. 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?

10. The resistance of the tertiary winding of a power transformer is 0.125 ohm at 25o C and the temperature coefficient of resistance at 25o C is 0.00393. What is the resistance at 65o C?

11. The resistance of a transformer windings is 0.25 ohm at 250 C. When operating at full load, the temperature of the winding is 750 C. The temperature coefficient of resistance of copper at 00 C is 4.27 x 10-3 per degree centigrade. What is the winding resistance at full load?
• α0 =  → T=1/α0

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