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GCE JAN 2008 : (AS 3) Systems and Control: Industrial and Commercial Practices

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ADVANCED SUBSIDIARY (AS) General Certificate of Education January 2008 Technology and Design assessing Unit 3: Systems and Control: Industrial and Commercial Practices ASV31 Assessment Unit AS 3 [ASV31] TUESDAY 29 JANUARY, MORNING TIME 1 hour 30 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number on the Answer Booklet provided and on the A3 pro forma answer pages provided. Answer all three questions. Answer to questions 3(b)(i) and (ii) should be made on the A3 pro forma answer page provided. INFORMATION FOR CANDIDATES The total mark for this paper is 60, including a maximum of 3 marks for quality of written communication. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. At the conclusion of the examination, attach the A3 pro forma answer pages securely to the Answer Booklet with the treasury tag supplied. ASV3W8 3219 1 (a) Fig. 1(a) shows a prototype for an electronic temperature sensing circuit where the user can select one of four settings. 6V R5 -t Rt SW Tr1 R1 R2 R3 R4 Vo 0V Fig. 1(a) State the type of switch SW shown in Fig. 1(a). [1] (b) The data in table, Fig. 1(b) shows the resistance of the thermistor Rt at a range of temperatures. Temperature ( C) Resistance of Rt (k ) 0 18 10 10 20 6 30 4 40 2 Fig. 1(b) (i) The thermistor Rt has a negative temperature coefficient. Briefly explain how this property is indicated by the data shown in Fig. 1(b). [1] (ii) Use the data from Fig. 1(b) to calculate the resistance of R2 in Fig. 1(a) required to make voltage Vo = 1.2 volts when the temperature is 10 C. [4] (iii) Briefly describe the operation of the circuit shown in Fig. 1(a) when the switch is at any one of the four settings. [3] ASV3W8 3219 2 [Turn over (c) The LEDs shown in Fig. 1(a) have a forward voltage rating of 2 volts. (i) Calculate the value of resistance for R5 required to limit the current in each LED to 20 mA. [2] (ii) Determine the maximum power dissipated by the resistor R5. [2] (d) Fig. 1(c) shows a float linked to a variable resistor, which is part of a system to warn when the level of liquid in a tank is low. When the tank is full the float moves up and the value for the variable resistor is 100 K. When the tank is empty the float moves down and the value for the variable resistor is 0 K. The associated circuit for the warning system is shown in Fig. 1(d). Variable resistor VR VR Float Tank Fig. 1(c) 9V R1 VR R3 X + 9 V Buzzer R2 0V 9 V Fig. 1(d) (i) Name the component labelled X in Fig. 1(d). [1] (ii) Describe the operation of the circuit shown in Fig. 1(d) for empty and full tank conditions. [5] ASV3W8 3219 3 [Turn over 2 (a) Pulleys may be used in simple lifting systems. (i) Vee belts are commonly used with pulleys. Name two other common belt types. [2] (ii) Calculate the effort required in a lifting system if the load is 80 N and the mechanical advantage is 1.8. [2] (iii) If the velocity ratio of the lifting system in 2(a)(ii) is 2 and the effort moves 1.5 m, calculate the distance moved by the load. [3] (iv) Using the information above calculate the efficiency of the lifting system. [3] (b) Name and draw a linkage which would transmit an input motion through a right angle to give an output motion. [4] (c) Fig. 2 shows part of a mechanical system. (i) Calculate the output speed of wormwheel X if the motor rotates at 480 rev/min. [2] (ii) Calculate the number of teeth on the wormwheel Y if it rotates at 6 rev/min. ASV3W8 3219 4 [3] [Turn over ASV3W8 3219 5 [Turn over X Wormwheel 40 Teeth N 35 Teeth C 160 Teeth B 80 Teeth Fig. 2 M 70 Teeth Y Wormwheel A 160 Teeth 480 rev/min Motor 3 Fig. 3 shows part of an incomplete pneumatic circuit. (a) (i) Name the activation method at A. [1] (ii) Briefly describe the effect that component B has on the operation of the circuit. [2] (b) (i) On the pro forma provided (answer number 3(b)(i) and (ii)), add any necessary components and complete the circuit to enable the double acting cylinder to outstroke once the air bleed has been activated. [5] (ii) On the pro forma provided (answer number 3(b)(i) and (ii)), add any necessary components and complete the circuit to enable the double acting cylinder to instroke after a delay in time. [5] (c) (i) Briefly describe why two double acting cylinders may produce different forces during the instroke with the same pistons sizes and air pressure. [3] (ii) The double acting cylinder shown in Fig. 3 produces a force during the outstroke of 1695.6 N and operates under a pressure of 0.6 N/mm2. Calculate the piston radius for the double acting cylinder. Please assume = 3.14. [3] ASV3W8 3219 6 [Turn over A Air bleed 14 12 5 1 3 B Fig. 3 THIS IS THE END OF THE QUESTION PAPER ASV3W8 3219 7 [Turn over S 11/06 302-004-1 8 [Turn over

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Additional Info : Gce Technology and Design January 2008 Assessment Unit AS 3, Unit 3 – Systems and Control: Industrial and Commercial Practices
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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