Basic Electrical Engineering
Unit 6: Work, Power, Energy and Batteries Explain the effect of temperature on the resistance of various materials. (6M) 2. Define resistance temperature coefficient of a conducting material and state its unit. 3. Also with usual notations prove that (α1- α2)= α 1* α 2(t2-t1). (6M) 4. Define insulation resistance. Derive expression for insulation resistance of a single core cable. (6M)5. Explain the construction of lead Acid battery(4M)6. Explain the charging of lead acid battery.What are the changes takes place during charging(4M)7. Describe the maintenance procedure of lead acid battery. (4M)8. State the functions of separator in lead acid battery(4M)9. Explain the various methods for battery charging. (6M)10. Explain the series ,parallel and series parallel grouping of battery(6M)11. Explain the construction of lithium Ion battery(4M)12. Explain the charging of lithium Ion battery.What are the changes takes place during charging(4M)13. Describe the maintenance procedure of lithium Ion battery(6M)14. Explain the depth of discharge of battery. (6M) 15. 4. A water pump lifts 50 
of water per hour to a height of 20 m. The overall efficiency of water pump set is 0.60. Find monthly bill, when the pump is used 4 hours a day for a month of 30 days, at a rate of Rs. 5/KWh. (6M) 16. 5. An electric kettle is required to raise the temperature of 2 litres of water from 
C to 
C in 15 mins. Calculate the resistance of heating element if the kettle is to be used on 200 V supply. Assume efficiency of the kettle to be 80 %. Assume specific heat of water of 4180 J/kg-K. (6M)17. 6. Find the current flowing at the instant of switching 40 W lamp on 240 V supply. Given that working temperature of filament is 
C and temp. Coefficient of resistance of filament at 
C is 0.005 O
. (6M)18. A pipe of silver wire has a resistance of 3 Ω. What will be the resistance of manganin wire one third of length & one third the diameter that or silver & the resistivity of manganin is 30 times that of silver. (6M)19. A single core cable has conductor diameter of 5cm & insulation thickness of 3 cm. The resistivity of copper & insulation is 1.70 x 10-8 Ω-m & 7x10-12 Ω-m respectively. Determine resistance of conductor & insulator of the cable for 200 m length. (6M)20. A single core cable has its conductor diameter as 2 cm & outer diameter as 5 cm. The resistivity of conductor & insulator are 1.73*10-8 Ω-m & 8*1012 Ω-m respectively. Calculate resistance of conductor and insulation for a cable of 100m length. (6M)21. A pump driven by a DC electric motor lifts 1.5m3 of water per minute to a height of 40m. The pump has an efficiency of 90% and the motor has an efficiency of 85%. Determine 1) The power input to the motor 2) The current taken from a 480V supply. Assume the mass of 1m3 of water is 1000kg. (6M)22. A motor pump set lifts a 1200 m3 of water to a height 15m/hr. If efficiency of motor is 80% and that of pump is 75%. Calculate the monthly bill of set if it is used 4 hrs/day for 30 days at the rate of 5 rs/unit. (6M)23. An electrically driven pump lifts 100 m3 of water per minute through a height of 15 m. allowing an overall efficiency of 70٪ for the motor and pump, calculate the input power to motor. If the pump is in operation for an average of 2 hours per day for 30 days, calculate the energy consumption in KWH and cost of energy at the rate of Rs 5 per KWH. Take 1 m3 of water has a mass of a 1000Kg and g=9.81 m/s2. (6M)24. A coil of insulated copper wire has a resistance of 150Ω at 20°c. When coil is connected across a 240V supply the current after several hours is 1.25A. Calculate the temp of coil assuming the temperature coefficient of resistance of copper at 20°c to be 0.0039°c. (6M)25. A copper conductor has specific resistance of 1.6*106Ω-cm. at 0°c & R.T.C 1/254.5 /°c at 20°c. then find (i)Specific resistance at 60°c (ii) R.T.C.at 60°c(6M)26. Field coil of DC motor takes a current of 1.6A from 400V supply, after running for several hours. If temperature rise is 200C, what extra resistance is required in the field circuit to maintain a field current equal to 2A? Assume the motor is started from cold at 100C and RTC at 100C is 0.0034/0. (6M)27. The filament of 240V of metal filament lamp is to be constructed from a wire having a diameter of 0.03mm and resistivity of 4.3μΩ-cm. If the R.T.C of the filament material is 0.005/°C at 20°C, what length of the filament is necessary for the lamp to dissipate 60W at a filament temperature of 2420°C. Assume room temperature as 20°C. (6M)28. A single core cable has its conductor diameter as 2 cm & outer diameter as 5 cm. The resistivity of conductor & insulator are 1.73*10-8 Ω-m & 8*1012 Ω-m respectively. Calculate resistance of conductor and insulation for a cable of 100m length. (6M)
of water per hour to a height of 20 m. The overall efficiency of water pump set is 0.60. Find monthly bill, when the pump is used 4 hours a day for a month of 30 days, at a rate of Rs. 5/KWh. (6M) 16. 5. An electric kettle is required to raise the temperature of 2 litres of water from C to C in 15 mins. Calculate the resistance of heating element if the kettle is to be used on 200 V supply. Assume efficiency of the kettle to be 80 %. Assume specific heat of water of 4180 J/kg-K. (6M)17. 6. Find the current flowing at the instant of switching 40 W lamp on 240 V supply. Given that working temperature of filament is C and temp. Coefficient of resistance of filament at C is 0.005 O. (6M)18. A pipe of silver wire has a resistance of 3 Ω. What will be the resistance of manganin wire one third of length & one third the diameter that or silver & the resistivity of manganin is 30 times that of silver. (6M)19. A single core cable has conductor diameter of 5cm & insulation thickness of 3 cm. The resistivity of copper & insulation is 1.70 x 10-8 Ω-m & 7x10-12 Ω-m respectively. Determine resistance of conductor & insulator of the cable for 200 m length. (6M)20. A single core cable has its conductor diameter as 2 cm & outer diameter as 5 cm. The resistivity of conductor & insulator are 1.73*10-8 Ω-m & 8*1012 Ω-m respectively. Calculate resistance of conductor and insulation for a cable of 100m length. (6M)21. A pump driven by a DC electric motor lifts 1.5m3 of water per minute to a height of 40m. The pump has an efficiency of 90% and the motor has an efficiency of 85%. Determine 1) The power input to the motor 2) The current taken from a 480V supply. Assume the mass of 1m3 of water is 1000kg. (6M)22. A motor pump set lifts a 1200 m3 of water to a height 15m/hr. If efficiency of motor is 80% and that of pump is 75%. Calculate the monthly bill of set if it is used 4 hrs/day for 30 days at the rate of 5 rs/unit. (6M)23. An electrically driven pump lifts 100 m3 of water per minute through a height of 15 m. allowing an overall efficiency of 70٪ for the motor and pump, calculate the input power to motor. If the pump is in operation for an average of 2 hours per day for 30 days, calculate the energy consumption in KWH and cost of energy at the rate of Rs 5 per KWH. Take 1 m3 of water has a mass of a 1000Kg and g=9.81 m/s2. (6M)24. A coil of insulated copper wire has a resistance of 150Ω at 20°c. When coil is connected across a 240V supply the current after several hours is 1.25A. Calculate the temp of coil assuming the temperature coefficient of resistance of copper at 20°c to be 0.0039°c. (6M)25. A copper conductor has specific resistance of 1.6*106Ω-cm. at 0°c & R.T.C 1/254.5 /°c at 20°c. then find (i)Specific resistance at 60°c (ii) R.T.C.at 60°c(6M)26. Field coil of DC motor takes a current of 1.6A from 400V supply, after running for several hours. If temperature rise is 200C, what extra resistance is required in the field circuit to maintain a field current equal to 2A? Assume the motor is started from cold at 100C and RTC at 100C is 0.0034/0. (6M)27. The filament of 240V of metal filament lamp is to be constructed from a wire having a diameter of 0.03mm and resistivity of 4.3μΩ-cm. If the R.T.C of the filament material is 0.005/°C at 20°C, what length of the filament is necessary for the lamp to dissipate 60W at a filament temperature of 2420°C. Assume room temperature as 20°C. (6M)28. A single core cable has its conductor diameter as 2 cm & outer diameter as 5 cm. The resistivity of conductor & insulator are 1.73*10-8 Ω-m & 8*1012 Ω-m respectively. Calculate resistance of conductor and insulation for a cable of 100m length. (6M) 
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