Official June 2024 AQA A-level PHYSICS 7408/3BE Paper 3 Section B Electronics Merged Question Paper + Mark Scheme + Insert Ace your Mocks!!! *JUN2474083BE01* IB/M/Jun24/E8 7408/3BE For Examiner’s Use Question Mark 1 2 3 4 5 TOTAL Monday 17 June 2024 Morning Materials For this paper you must have: • a pencil and a ruler • a scientific calculator • a Data and Formulae Booklet • a protractor. Instructions • Use black ink or black ball-point pen. • Fill in the boxes at the top of this page. • Answer all questions. • You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. • If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s). • Do all rough work in this book. Cross through any work you do not want to be marked. • Show all your working. Information • The marks for questions are shown in brackets. • The maximum mark for this paper is 35. • You are expected to use a scientific calculator where appropriate. • A Data and Formulae Booklet is provided as a loose insert. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level PHYSICS Paper 3 Section B Electronics Time allowed: The total time for both sections of this paper is 2 hours. You are advised to spend approximately 50 minutes on this section. 2 *02* IB/M/Jun24/7408/3BE Do not write outside the Section B box Answer all questions in this section. 0 1 A toy manufacturer is designing a two-tone siren for use in small battery-operated cars. Figure 1 shows design Option 1. Option 1 uses three separate signal generators feeding into a logic sub-system. The signal generators produce logic-compatible 9 V square waves of frequencies 1024 Hz, 1 Hz and 512 Hz. Figure 1 The waveforms shown are not to scale. 0 1 . 1 Explain how the logic level applied at B in Figure 1 determines the output frequency at Q. [2 marks] 0 1 . 2 Write the Boolean algebra expression for output Q in terms of the inputs A, B and C. Use only the logic operations shown in Figure 1. [2 marks] Q = 3 *03* Turn over ► IB/M/Jun24/7408/3BE Do not write outside the 0 1 box . 3 Option 1 is tested by replacing the 1 Hz signal generator with a manual input. The manual input is provided by the combination of a push-to-make switch and a 10 kΩ resistor. The combination produces the following voltages at its output: • 0 V when the switch is not pressed • 9 V when the switch is pressed. Figure 2 shows the symbol for the push-to-make switch. Figure 2 Complete Figure 3 to show how this switch and the 10 kΩ resistor are connected. Label the output Vout. You do not need to add details taken from Figure 1. [1 mark] Figure 3 Question 1 continues on the next page 4 *04* IB/M/Jun24/7408/3BE Do not write outside the 0 1 box . 4 Figure 4 shows a generalised layout of an integrated circuit (IC) for an N-bit binary counter. Q0 is the output that provides the least significant bit. Figure 4 A signal generator feeds a square wave of frequency 1024 Hz into the clock of the IC. The N-bit binary counter generates the 512 Hz signal and the 1 Hz signal from separate outputs. Deduce which of the outputs Q0 to QN will provide the 1 Hz signal. [1 mark] 5 *05* Turn over ► IB/M/Jun24/7408/3BE Do not write outside the 0 1 box . 5 To make the two-tone siren, the manufacturer decides to use a new design, Option 2. Option 2 contains: • one 1024 Hz signal generator • one N-bit binary counter • a new logic sub-system as shown in Figure 5. Figure 5 Assume that: • each type of logic gate has its own dedicated IC chip • each separate signal generator is based upon its own IC chip. Compare the number of ICs used in Option 1 with the number used in Option 2. Go on to explain one advantage of the manufacturer’s decision. [2 marks] 8 6 *06* IB/M/Jun24/7408/3BE Do not write outside the 0 2 The short message service (SMS) on a mobile phone can send a maximum box of 160 characters per message. Each character is represented by its own seven-bit binary code as it is converted to digital data. 0 2 . 1 The mobile phone transmits digital data at a rate of 8 kilobytes per second (kB s−1 ) when using the SMS function. Determine the minimum time required to send 160 characters. [2 marks] time = s Electrical noise can affect communication systems. 0 2 . 2 Describe one origin of electrical noise in a communication system. [1 mark] 0 2 . 3 Describe the effect that electrical noise can have: • on the signal and • on the communication system. [2 marks] 7 *07* Turn over ► IB/M/Jun24/7408/3BE Do not write outside the box Figure 6 shows a noisy digital signal Vin which is applied to a circuit. The circuit output Vout switches to: • 5 V when the input voltage Vin falls below 1.8 V • 0 V when the input voltage Vin rises above 3.2 V. 0 2 . 4 Draw, on Figure 7, the output signal Vout from the circuit. Assume that Vout is initially at 5 V