- 1 A Kitchen In A Residential Area Has The Following Appliances Connected To A 120v Dc Supply And A Circuit Breaker One 1 (158.37 KiB) Viewed 16 times
N.B: You MUST draw the circuit first with theID values which is 43705 before starting the solution.
1. A kitchen in a residential area has the following appliances connected to a 120V DC supply and a circuit breaker: one (20xd) W electric kettle, one (500xb) W toaster and one (700xe) W dish washer. (1) Apply information learn in electrical circuits to draw the schematic diagram and analyze to find [5] out the rating of the circuit breaker (0 to 15 A, 15.1 to 30 A, 30.1 to 60 A, 60.1 to 100 A) so that all appliances can be operated at the same time without tripping the circuit breaker? Provide necessary calculation to justify your answer. (ii) The house owner now wants to buy a new induction stove of (900xc) W for the kitchen due to [5] low gas supply. Apply your concept to find out if it would be feasible for the owner to buy the new induction stove with the existing connection of part (i)? Show proper logic behind your answer. If you feel that the new appliance would not be fitted to the kitchen, but it is necessary to be installed, then can you propose a new model for the kitchen? (iii) For the circuit drawn in part (1), compute the value of the resistances, the number of electrons, [8] and the energy dissipated to each of the three loads if the circuit is on for (e+2) hours. What is the total cost (@ 12 tk/kWhr) if all the appliances are used for three hours? 2. (1) Determine the resistance at 30°C of an 80 ft of telephone wire if the diameter is 0.034 inch. [3] Choose the material as Copper if (d+e) is an even number and Aluminum if (d+e) is an odd number. Use table 1 for Resistivity (p). (ii) What is the value of the resistance of part (1) if the area is increased by a factor three (3) and [3] the length is halved while the temperature remains constant? (iii) What is the value of the resistance of part (1) if the temperature is increased to 90°C? Use table 2 for Infrared Absolute Temperature ([T;]). [3] (iv) Explain briefly the reason for the change in part (iii). Table 1 Resistivity (r) of various materials. Material Silver Copper Gold Aluminum Tungsten Nickel Iron Tantalum Nichrome Tin oxide Carbon Ω-cm 1.645 × 10-6 1.723 x 10-6 2.443 x 10-6 2.825 x 10-6 5.485 x 10-6 7.811 x 10-6 12.299 × 10-6 15.54 x 10-6 99.72 x 10-6 250 x 10-6 3500 × 10-6 Table 2 Inferred absolute temperatures (T). Material Silver Copper Gold Aluminum Tungsten Nickel Iron Nichrome Constantan °C -243 -234.5 -274 -236 -204 -147 -162 -2,250 -125,000 [3]