2 (a) An alloy wire with 4.0 mm diameter has resistance of 50 1 at a temperature of 20 °C. Determine: (i) the length of

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2 A An Alloy Wire With 4 0 Mm Diameter Has Resistance Of 50 1 At A Temperature Of 20 C Determine I The Length Of 1 (77.67 KiB) Viewed 21 times

2 (a) An alloy wire with 4.0 mm diameter has resistance of 50 1 at a temperature of 20 °C. Determine: (i) the length of the alloy wire, given that the resistivity of the alloy material (2 marks) is 3.14 x 10 m; (ii) the wire resistance at 40°C if the temperature coefficient of the alloy (2 marks) material at 20°C is 0.07 °C! (b) A production machine operates for 8 hours per day. The machine with power rating of 1200W worked for 25 days in last month and the supply voltage to the machine is 250V. If the electricity charge is HK$1.25 per kWh, please response to the following questions: (1) Determine the supply current for the production machine; and (1 mark) (ii) Calculate the electricity bill for last month. (2 marks) (iii) As the industrial plant operations are costly especially for the electricity (8 marks) use, proposed 4 methods that help reducing the energy cost for typical plants in Hong Kong environment. (c) For the circuit shown in Figure 2(c), determine: (i) the total resistance, Rt; (3 marks) (ii) the supply current, It; (2 marks) (iii) the branch current, 13, and (3 marks) (iv) the potential difference V across the resistor Ro- (2 marks) IT R2 20092 16 w 13 R6 E 40V R 10092 R3 M w 30092 V6 55092 R4 M 16022 R5 M 45022 Figure 2(c)