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C14 ee-106-basic electrical engineering

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Srinivasa Rao
Srinivasa Rao

This document contains an exam for a basic electrical engineering diploma. It consists of two parts: Part A contains 10 multiple choice questions worth 4 marks each, and Part B contains 4 long-form questions worth 10 marks each. The questions cover topics like Ohm's law, resistor circuits, electric power, heating effects, magnetism, electromagnetic induction, capacitors, and more. The exam is worth a total of 80 marks and lasts 3 hours.

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046 046 046 046 * * * C14–EE–106 4046 BOARD DIPLOMA EXAMINATION, (C–14) OCT/NOV—2016 DEEE—FIRST YEAR EXAMINATION BASIC ELECTRICAL ENGINEERING Time : 3 hours ] [ Total Marks : 80 PART—A 4×10=40 Instructions : (1) Answer all questions. (2) Each question carries four marks. 1. (a) List any two limitations of Ohm’s law. 2 (b) Define the terms conductance and conductivity. 2 2. (a) Write the expression for equivalent resistance when three resistors are connected in parallel. 2 (b) What are the factors on which the resistance of a conductor depends? 2 3. (a) Give the expression and unit of electrical power. 2 (b) Define electrical energy and give its unit. 2 4. (a) State Joule’s law of heating. 2 (b) List any four applications of heating effects of electric current. 2 5. (a) State right-hand thumb rule. 2 (b) Give expression for field strength (i) at the centre of circular conductor and (ii) at any point on the axis of a circular conductor. 2 /4046 1 [ Contd... * 4 0 4 6 *
046 046 046 046 * * * 6. (a) State Fleming’s left-hand rule. 2 (b) Define magnetic flux and magnetic flux density. Mention their units. 2 7. (a) State Faraday’s 1st law of electromagnetic induction. 2 (b) A coil of 250 turns is linked with a flux of 0·025 Wb, when carrying a current of 25 A. Calculate the inductance of the coil. 2 8. (a) State Lenz’s law. 2 (b) Write the expressions for the self-inductance and mutual inductance. 2 9. (a) State Coulomb’s 2nd law of electrostatics. 2 (b) List any four uses of a capacitor. 2 10. (a) Write an expression for energy stored in a capacitor. 2 (b) Plot electrostatic field due to isolated positive charge and isolated negative charge. 2 PART—B 10×4=40 Instructions : (1) Answer any four questions. (2) Each question carries ten marks. 11. (a) Calculate the length of copper wire 1·5 mm in diameter to have a resistance of 0·3 ohm, given that resistivity of copper is 0·017 m W-m. 4 (b) The resistance of a coil of wire increases from 40 ohms at 10 ºC to 48·25 ohms at 60 ºC. (i) Find the temperature coefficient of resistance at 0 ºC (ii) Find the resistance of coil at 0 ºC 6 /4046 2 [ Contd...
046 046 046 046 * * * 12. (a) Distinguish among conductor, insulator and semi- conductor w.r.t valance electrons and give examples. 4+1=5 (b) Two resistances 50 ohms and 10 ohms are connected in parallel and draw a current of 20A from the supply. Determine the current in each branch and supply voltage. 5 13. (a) Calculate the input of an electric motor when the output is 10 HP and the efficiency of the motor is 90%. 3 (b) Calculate electricity bill for the month of June at R 1·20 per unit for a residential building with the following loads. The meter rent per month is R 20 : 7 (i) 10 Nos. of 40 watt tubelights used for 10 hr/day (ii) 8 Nos. of 80 watt fans used for 12 hr/day (iii) 1 No. of 250 watt refrigerator used for 12 hr/day (iv) 1 No. of 1000 watt heater working for 1hr/day (v) 1 No. of 450 watt electric iron working for 1 hr/day 14. (a) Define thermal efficiency. 2 (b) The heater element of an electric kettle has a constant resistance of 100 ohms and the applied voltage is 250 V. Calculate the time taken to raise the temperature of one litre of water from 15 ºC to 90 °C, assuming that 85% of the power input to the kettle is usefully employed, if the water equivalent of the kettle is 100 grams. 8 15. (a) A straight long conductor of 1 meter length carrying a current 60 A is placed at right angle to a uniform magnetic field to strength 2·5 Wb/m2 . Determine the mechanical force acting on the conductor. 3 (b) A circular iron ring having a mean diameter of 30 cm and cross-sectional area of 4 cm2 is uniformly wound with 1000 turns of wire. A radial saw cut of 1 mm is made in the ring. Determine the current which will produce a flux of 0·4 m-Wb in the air gap. Assume the relative permeability under these conditions to be 941. Neglect leakage and fringing. 7 /4046 3 [ Contd...
046 046 046 046 * * * 16. (a) Explain the concept of self-induced e.m.f. 5 (b) The combined inductances of two coils connected in series are 0·6 H and 0·1 H. Depending on the relative directions of the currents in the coils, if one of the coils, when isolated, has a self-inductance of 0·2 H, calculate— (i) the mutual inductance; (ii) the coupling coefficient. 5 17. (a) Derive an expression for energy stored in a magnetic field. 5 (b) An iron ring has a cross-section of 20 cm2 and a mean length of 120 cm is wound with 300 turns. The permeability of iron is 800. If the current in the coil is 10 A, calculate— (i) the inductance; (ii) energy stored in joules. 5 18. (a) Three capacitors of 2 micro-farad, 4 micro-farad and 6 micro-farad are connected in series across a 220-V d.c. supply. (i) Find the total capacitance. (ii) Find charge on each capacitor. (iii) Find potential difference across each capacitor. 6 (b) Two small balls having charges one double the other are placed at a distance of 0·5 m apart in air. If the repulsive force between the balls is 2·75 N, determine the charge on each ball. 4 H H H /4046 4 AA6(T)—PDF

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C14 ee-106-basic electrical engineering

  • 1. 046 046 046 046 * * * C14–EE–106 4046 BOARD DIPLOMA EXAMINATION, (C–14) OCT/NOV—2016 DEEE—FIRST YEAR EXAMINATION BASIC ELECTRICAL ENGINEERING Time : 3 hours ] [ Total Marks : 80 PART—A 4×10=40 Instructions : (1) Answer all questions. (2) Each question carries four marks. 1. (a) List any two limitations of Ohm’s law. 2 (b) Define the terms conductance and conductivity. 2 2. (a) Write the expression for equivalent resistance when three resistors are connected in parallel. 2 (b) What are the factors on which the resistance of a conductor depends? 2 3. (a) Give the expression and unit of electrical power. 2 (b) Define electrical energy and give its unit. 2 4. (a) State Joule’s law of heating. 2 (b) List any four applications of heating effects of electric current. 2 5. (a) State right-hand thumb rule. 2 (b) Give expression for field strength (i) at the centre of circular conductor and (ii) at any point on the axis of a circular conductor. 2 /4046 1 [ Contd... * 4 0 4 6 *
  • 2. 046 046 046 046 * * * 6. (a) State Fleming’s left-hand rule. 2 (b) Define magnetic flux and magnetic flux density. Mention their units. 2 7. (a) State Faraday’s 1st law of electromagnetic induction. 2 (b) A coil of 250 turns is linked with a flux of 0·025 Wb, when carrying a current of 25 A. Calculate the inductance of the coil. 2 8. (a) State Lenz’s law. 2 (b) Write the expressions for the self-inductance and mutual inductance. 2 9. (a) State Coulomb’s 2nd law of electrostatics. 2 (b) List any four uses of a capacitor. 2 10. (a) Write an expression for energy stored in a capacitor. 2 (b) Plot electrostatic field due to isolated positive charge and isolated negative charge. 2 PART—B 10×4=40 Instructions : (1) Answer any four questions. (2) Each question carries ten marks. 11. (a) Calculate the length of copper wire 1·5 mm in diameter to have a resistance of 0·3 ohm, given that resistivity of copper is 0·017 m W-m. 4 (b) The resistance of a coil of wire increases from 40 ohms at 10 ºC to 48·25 ohms at 60 ºC. (i) Find the temperature coefficient of resistance at 0 ºC (ii) Find the resistance of coil at 0 ºC 6 /4046 2 [ Contd...
  • 3. 046 046 046 046 * * * 12. (a) Distinguish among conductor, insulator and semi- conductor w.r.t valance electrons and give examples. 4+1=5 (b) Two resistances 50 ohms and 10 ohms are connected in parallel and draw a current of 20A from the supply. Determine the current in each branch and supply voltage. 5 13. (a) Calculate the input of an electric motor when the output is 10 HP and the efficiency of the motor is 90%. 3 (b) Calculate electricity bill for the month of June at R 1·20 per unit for a residential building with the following loads. The meter rent per month is R 20 : 7 (i) 10 Nos. of 40 watt tubelights used for 10 hr/day (ii) 8 Nos. of 80 watt fans used for 12 hr/day (iii) 1 No. of 250 watt refrigerator used for 12 hr/day (iv) 1 No. of 1000 watt heater working for 1hr/day (v) 1 No. of 450 watt electric iron working for 1 hr/day 14. (a) Define thermal efficiency. 2 (b) The heater element of an electric kettle has a constant resistance of 100 ohms and the applied voltage is 250 V. Calculate the time taken to raise the temperature of one litre of water from 15 ºC to 90 °C, assuming that 85% of the power input to the kettle is usefully employed, if the water equivalent of the kettle is 100 grams. 8 15. (a) A straight long conductor of 1 meter length carrying a current 60 A is placed at right angle to a uniform magnetic field to strength 2·5 Wb/m2 . Determine the mechanical force acting on the conductor. 3 (b) A circular iron ring having a mean diameter of 30 cm and cross-sectional area of 4 cm2 is uniformly wound with 1000 turns of wire. A radial saw cut of 1 mm is made in the ring. Determine the current which will produce a flux of 0·4 m-Wb in the air gap. Assume the relative permeability under these conditions to be 941. Neglect leakage and fringing. 7 /4046 3 [ Contd...
  • 4. 046 046 046 046 * * * 16. (a) Explain the concept of self-induced e.m.f. 5 (b) The combined inductances of two coils connected in series are 0·6 H and 0·1 H. Depending on the relative directions of the currents in the coils, if one of the coils, when isolated, has a self-inductance of 0·2 H, calculate— (i) the mutual inductance; (ii) the coupling coefficient. 5 17. (a) Derive an expression for energy stored in a magnetic field. 5 (b) An iron ring has a cross-section of 20 cm2 and a mean length of 120 cm is wound with 300 turns. The permeability of iron is 800. If the current in the coil is 10 A, calculate— (i) the inductance; (ii) energy stored in joules. 5 18. (a) Three capacitors of 2 micro-farad, 4 micro-farad and 6 micro-farad are connected in series across a 220-V d.c. supply. (i) Find the total capacitance. (ii) Find charge on each capacitor. (iii) Find potential difference across each capacitor. 6 (b) Two small balls having charges one double the other are placed at a distance of 0·5 m apart in air. If the repulsive force between the balls is 2·75 N, determine the charge on each ball. 4 H H H /4046 4 AA6(T)—PDF