2013 CAIE AS & A level October November Physics Paper 21 Q. No. 6 (9702/21/O/N/13) by Sajit C Shakya

2013 CAIE AS & A level October November Physics Paper 21 Q. No. 6 (9702/21/O/N/13) by Sajit Chandra Shakya from Nepal Chapter - CURRENT ELECTRICITY (a) Define potential difference (p.d.). A power supply of e.m.f. 240 V and zero internal resistance is connected to a heater as shown in Fig. 6.1. The wires used to connect the heater to the power supply each have length 75 m. The wires have a cross-sectional area 2.5 mm2 and resistivity 18 nΩm. The heater has a constant resistance of 38Ω. (i) Show that the resistance of each wire is 0.54Ω. (ii) Calculate the current in the wires. (iii) Calculate the power loss in the wires. (c) The wires to the heater are replaced by wires of the same length and material but having a cross-sectional area of 0.50 mm2. Without further calculation, state and explain the effect on the power loss in the wires.