GCSE Electronics June 2007 Paper

For this paper you must have: ! a pencil and a ruler ! a calculator. General Certificate of Secondary Education June 2007 ELECTRONICS 3432/F Written Paper Foundation Tier Thursday 24 May 2007 1.30 pm to 3.00pm Time allowed: 1 hour 30 minutes Instructions ! Use blue or black ink or ball-point pen. ! Fill in the boxes at the top of this page. ! Answer all questions. ! Answer the questions in the spaces provided. ! Show the working of your calculations. Information ! The maximum mark for this paper is 120. ! The marks for questions are shown in brackets. ! A list of formulae and other information, which you may wish to use in your answers, is provided on page 2. ! You are expected to use a calculator where appropriate. ! You are reminded of the need for good English and clear presentation in your answers. M/Jun07/3432/F F 3432/F For Examiners Use Surname Other Names Centre Number Candidate Number Candidate Signature For Examiners Use Question Mark Question Mark 1 9 2345678 Total (Column 1) Total (Column 2) TOTAL Examiners Initials2 M/Jun07/3432/FTurn over! 3 LEAVE MARGIN BLANK M/Jun07/3432/F Answer all questions in the spaces provided. 1 (a) What component can be used to obtain a safe low voltage from the mains supply? ............................................................................................................................................ (1 mark) (b) Name two components that can be used to protect a circuit from a current overload. 1 .......................................................................................................................................... 2 .......................................................................................................................................... (2 marks) (c) State the colours of these wires in a three-pin mains plug. (i) Earth ........................................................................................................................... (ii) Live ............................................................................................................................ (iii) Neutral........................................................................................................................ (3 marks) (d) To help prevent accidents whilst working on electronics projects, state two measures that students should take. 1 .......................................................................................................................................... 2 .......................................................................................................................................... (2 marks) (e) State two effects on the human body of a large electric current. 1 .......................................................................................................................................... 2 .......................................................................................................................................... (2 marks) ____ 104 LEAVE MARGIN BLANK M/Jun07/3432/F 2 For each component named below, draw its symbol and describe its function. (10 marks) ____ 10 name symbol function resistor .................................................. .................................................. diode .................................................. .................................................. thermistor .................................................. .................................................. capacitor .................................................. .................................................. loudspeaker .................................................. ..................................................Turn over! 5 LEAVE MARGIN BLANK M/Jun07/3432/F 3 The diagram below shows a digital light meter system. The light level is measured, and its value is then displayed. (a) Which block represents (i) an input, ................................................................................................................... (ii) an output, ................................................................................................................... (iii) an analogue process, ................................................................................................. (iv) a digital process? ...................................................................................................... (4 marks) (b) In which block could (i) a D-type flip-flop be used, ........................................................................................ (ii) an LDR be used, ........................................................................................................ (iii) an op-amp be used, ................................................................................................... (iv) a 7-segment display be used? ................................................................................... (4 marks) (c) Which block (i) is a simple memory, .................................................................................................. (ii) could use LEDs? ....................................................................................................... (2 marks) Turn over for the next question ____ 10 light sensor ADC latch display6 LEAVE MARGIN BLANK M/Jun07/3432/F 4 (a) Label the three different types of logic gate in the diagram below. (3 marks) (b) Complete the truth table below to describe the operation of the circuit in part (a). (6 marks) (c) The inputs A and B are connected to beam sensors across a road as shown below. The sensors give a logic 1 when the beam is broken. A lorry is shown travelling towards the sensors. On the diagram above, draw the position of the lorry when the output of the system, Q, first gives a logic 1. (1 mark) ____ 10 A B C D Q 0 0 0 0 1 1 1 0 1 1...................................................... ...................................................... ................................ A C Q D B Sensor B Sensor ATurn over! 7 LEAVE MARGIN BLANK M/Jun07/3432/F 5 A project circuit requires a stable 5V power supply. For this a student uses a 12V battery which will discharge down to 9V towards the end of its useful life. (a) What type of component can produce a stable output voltage from a varying input voltage? ....................................................................................................................................... (1 mark) (b) Complete the circuit diagram below to show how this component is used for this function. Label the output of your circuit, and include a capacitor that will remove output noise. (5 marks) (c) The project circuit draws a current of 0.25A at 5V. Calculate (i) the overall resistance of the project circuit, ................................................................................................................................... (ii) the power consumption of the project circuit. ................................................................................................................................... (4 marks) ____ 10 +9V to 12V battery8 LEAVE MARGIN BLANK M/Jun07/3432/F 6 (a) Label the block diagram of a simple radio receiver system shown below. Use the following terms aerial af amplifier demodulator loudspeaker tuned circuit. (5 marks) (b) In which sub-system would you expect to find (i) an audio amplifier IC, ............................................................................................... (ii) a signal diode, ........................................................................................................... (iii) a variable capacitor and an inductor (coil)? ................................................................................................................................... (3 marks) (c) The simple radio receiver system can only be used with amplitude modulation. On the axes below sketch a voltage time graph for this type of modulated wave. (2 marks) ____ 10 time VTurn over! 9 LEAVE MARGIN BLANK M/Jun07/3432/F 7 (a) A D-type flip-flop is used as a latch. (i) Name and label the two inputs with their full names. (ii) Label the output. (3 marks) (b) Describe the operation of a 4013 type D-type flip-flop. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (3 marks) (c) The D-type flip-flop can also function as a frequency divider. Complete the diagram below to show how two D-type flip-flops can divide an input signal by a factor of four. Label the input and output of your circuit and draw the wire links required. (4 marks) ____ 10 D QQ CK D QQ CK D QQ CK10 LEAVE MARGIN BLANK M/Jun07/3432/F 8 The flowchart describes the action of a traffic light system that is capable of reacting to the length of the queue of traffic. (a) Draw the correct flowchart symbols at the five places where they are missing. (5 marks) (b) Label on the flowchart a decision box, an input box, a loop, an output box and a process box. (5 marks) turn on red delay 20 s delay 3 s delay 20 s delay 30 s turn off red and amber, turn on green turn on amber Nstart input traffic sensor signal is sensor activated delay 3 s turn off green turn on amber Y turn off amberTurn over! 11 LEAVE MARGIN BLANK M/Jun07/3432/F (c) (i) From start how long does it take before the green light turns on? ................................................................................................................................... (ii) The traffic sensor is activated by a long queue of traffic. How does this alter the behaviour of the traffic light system compared to a short queue of traffic? ................................................................................................................................... (iii) How many times in one cycle of the flowchart is the amber light switched on? ................................................................................................................................... (iv) What is the total length of time the amber light is switched on in one cycle of the flowchart? ................................................................................................................................... (v) What is the length of time from when the red light switches on, to the next time it switches on if there is a long queue of traffic? ................................................................................................................................... (5 marks) (d) A pedestrian crossing system normally shows a green light to traffic and a red symbol to pedestrians. A button is pressed by a pedestrian wishing to cross the road. After a 10s delay the traffic lights change to red and the pedestrian is shown a green symbol. The pedestrian then has 15s to cross the road before the pedestrian symbol changes back to red. Complete the flowchart to show how this pedestrian crossing system operates. (5 marks) ____ 20 pedestrian signal red12 LEAVE MARGIN BLANK M/Jun07/3432/F 9 A student decides to construct a traffic light system similar to that described in Question 8 part (a) and part (b), using 555 IC monostables as the timing sub-systems. It is not necessary to have completed your answer to Question 8 before attempting this question. (a) Complete the circuit diagram below to show how the 555 IC should be connected to form a monostable. Include a timing resistor and capacitor, and any other components or connections required. Label the connection to the next stage. (8 marks) (b) The traffic light output transducers are high power LEDs which have a maximum forward voltage of 4V when conducting a maximum current of 450 mA. Explain why they cannot be directly coupled to the logic gates or the timer in the system. ....................................................................................................................................... (1 mark) +12V 0V +Vs reset output ground control voltage discharge threshold trigger 555 ICTurn over! 13 LEAVE MARGIN BLANK M/Jun07/3432/F (c) LEDs should always be operated with a series resistor. The supply voltage for the system is 12V. (i) Calculate the voltage across the series resistor. ........................................................ (ii) What current will flow through the series resistor? ................................................. (iii) Calculate the required value of the series resistor. ................................................................................................................................... (iv) What preferred value of resistor from the E24 series should be chosen here? ................................................................................................................................... (5 marks) (d) It is decided to use an npn bipolar transistor to drive the LED and its series resistor. Draw the circuit diagram for the LED and its driver. Label the leads of the transistor and include a component that will limit the current to the input of the driver circuit. (6 marks) Question 9 continues on the next page14 LEAVE MARGIN BLANK M/Jun07/3432/F (e) When the system is first switched on, the first 555 IC monostable is triggered to provide a signal to turn on the red light for 20 s. The output from this sub-system triggers a second 555 IC monostable to turn on the amber light for 3 s and also keep the red light on during this period. The red light driver sub-system operates when the 20 s timer or the 3 s timer is high. At the end of the 3 s period a third 555 IC monostable is triggered for a period of 20 s to operate the green light. A fourth 555 IC monostable is triggered at the end of this 20 s period to turn the amber light on for a further 3 s, after which the first monostable is triggered and the cycle is repeated. The amber light driver sub-system operates when either of the 3 s timers are high. Complete the system diagram below labelling the four 555 timers with their respective on times; drawing in two logic gates; labelling three lamp drivers; and mark the red, amber and green lights with R, A, and G. Label each sub-system and complete the connections between them. (10 marks) END OF QUESTIONS ____ 3015 M/Jun07/3432/F There are no questions printed on this page16 M/Jun07/3432/F There are no questions printed on this page Copyright © 2007 AQA and its licensors. All rights reserved.