GCSE Electronics. Scheme of Work

Transcription

1 GCSE Electronics Scheme of Work

2 Week Topic Detail Notes 1 Practical skills assemble a circuit using a diagram recognize a component from its physical appearance (This is a confidence building/motivating exercise so it is important time is allowed for all circuits to work.) 2 System design describe the functions of common input and output transducers a simple system has an input, process and output using lines between subsystems represents the flow of information Build a circuit such as a 555 stylus organ given a layout diagram and very straight forward instructions. To ensure all learners are successful be familiar with common faults. Use a kit to investigate input and output transducers. Name the transducers but do not explain their operation at this stage. Draw diagrams of the systems. Arrange in order cards with the names of subsystems on them. 3 System design recall that a signal is an electrical voltage or current representing information be aware that there are counting, timing, amplifying,, memory subsystems Investigate the type of subsystems used in Fi, alarms, calculators, etc. Use cards again. (leave ADC and DAC until later) Hi 4 Logic explain the use of gates know that the state of the single output of a gate depends on the states of the inputs know that in a digital system the voltage of the signal is either high or low, 1 or 0 Use a kit, or other system to investigate gates. Deduce and record truth tables. Also use written examples. 5 Combinational use truth tables to determine the output of up to four gates solve problems stated in words using gates solve system problems with up to three inputs Paper based exercises and practical investigation kit or prototyping board. 6 Basic principles use the fact that the sum of voltages in a series circuit is equal to the supply voltage use the fact that the voltage across all parallel is the same use the fact that the current is the same everywhere in a series circuit use the fact that the total current entering a junction is equal to the total current leaving it Practical investigation of series and parallel circuits using batteries and lamps. Testing conductors and insulators. Finally explain the appearance of two lamps in parallel with each other and in series with a third lamp. klm Copyright 2009 AQA and its licensors. All rights reserved. 1

3 7 Basic principles know the definitions and units for current, voltage and resistance draw and interpret circuits using standard symbols use test instruments - voltmeters and ammeters use Ohm s law to calculate resistance Practical investigation using batteries, resistors and meters. Start with low value resistors - but be aware of power dissipation issues. Answer written examples. 8 Passive (resistors) interpret the markings on a resistor using the colour code and BS1852 code select an appropriate preferred value use a test instrument i.e. multimeter Provide the colour code in exam (or more colourful) format. Read the value of a resistor and check against multimeter measurements 9 Basic principles use Ohm s law for higher values of resistance kilohms and milliamps. Prefixes and powers of 10 use calculators scientific mode Practical investigations using batteries, resistors and multimeter. Paper based examples 10 Recap of Systems, Logic and Basic principles 11 Passive 12 Sequential Practical skills 13 Passive revision of work so far explain the use of switches select switches for different applications explain the use and application of pull up and pull down resistors describe the operation of the 4013 dual D- type flip-flop as a latch using S and R inputs. assemble a circuit explain the function of a D type flip-flop as a data latch. describe charge in the context of a capacitor as a device to store charge know different types of capacitor interpret the markings on capacitor value, tolerance, voltage rating and polarity know the unit of capacitance is the farad and use prefixes and powers of 10 explain the difference in applications and use of polarized and non-polarized capacitors Assessment of learning using exam style questions Investigate with prototyping boards and voltmeters. Build a circuit such as a quiz game referee using a chip, a 4013 and pull down resistors to develop confidence and to make it clear that electronic systems have a purpose. Investigate large value capacitors as charge storing devices discharge through LEDs and small motors. Charge capacitors through resistors and demonstrate that charging time depends on values of R and C. 2 Copyright 2009 AQA and its licensors. All rights reserved. klm

4 14 Electrical safety dangers of electricity effects on the human body outline the procedures for dealing with a casualty 15 Basic principles use the formula to calculate power P = I V select with appropriate power or current ratings for a given application 16 Electrical safety explain why an individual should not work alone know how to summon help carry out a risk assessment explain the need for PAT testing explain why may become hot explain capacitors may hold a lethal charge Measure skin resistance. Van de Graaff and demountable transformer could be used to demonstrate effects of high voltage and current. Carry out calculations on resistors and fuses. Use a catalogue to select appropriate values. Safety DVD if available. Demonstrate electrical heating. 17 Electrical safety devices 18 Monostable generator 19 Astable generators know the purpose and limitations of fuses and thermal and magnetic circuit breakers. calculate the value for a circuit breaker wire a three pin plug know that a transformer can produce a low voltage supply from the mains supply use and explain the application of a 555 integrated circuit in monostable mode use the formulae for time period T = 1.1 R C practice use of calculator use and explain the application of a 555 integrated circuit in astable mode use the formula for the period T = (R 1 + 2R 2 ) C/1.44 practice use of calculator Examine various circuit breakers. Wire three pin plugs safely. Carry out calculations. Recap of pull up resistors. Build and test a monostable with a measurable time period and compare with the calculated value. Investigate the need for a capacitor on the trigger input. Build and test an astable. Vary frequency use an LED and loudspeaker as an output. 20 Basic principles recap Ohm s Law use a light emitting diode and calculate the value of the series resistor Justify the values of the series resistors used in the monostable and astable circuits. klm Copyright 2009 AQA and its licensors. All rights reserved. 3

5 21 Basic principles know the unit of frequency is hertz use frequency = 1/period use test instruments - oscilloscope Use the astable circuit for oscilloscope measurements of period and voltage. 22 Sequential explain the function of the D type flip flop as a frequency divider recognize and draw timing diagrams for frequency dividers Use the astable as an input to a 4013 circuit and use LEDs to display division by 2 and 4 23 Basic principles calculate the effective resistance of up to four resistors in series calculate the effective resistance of two resistors in parallel Connect resistors in series and parallel on prototyping board and both measure and calculate their combined resistance. 24 Active 25 Active 26 Passive know that a bipolar transistor is 3 lead device and name the leads explain how an NPN transistor can be used as a switch explain why a base resistor is needed know that a MOSFET is 3 lead device and name the leads explain how a MOSFET can be used as a switch compare the advantages and disadvantages of MOSFETs and bipolar transistors explain what a relay is and that a diode is needed in a switching circuit to protect the MOSFET or bipolar transistor know that diodes are needed for other inductive loads such as motors or solenoid. Build a switching circuit on prototyping board with a non-inductive load. Show that the current through fingers is sufficient to switch a Darlington pair Build a switching circuit on prototyping board with a non-inductive load. Show that the current through fingers is sufficient to switch a MOSFET. Explain the relay including NO and NC contacts. Demonstrate the emf induced when the current through an inductor is switched off. - use neon lamp or give learners the opportunity to receive a shock from a 60 turn coil, iron core and 1.5 V cell (following risk assessment). 27 revision for exam. 28 revision for exam 29 end of year exam 4 Copyright 2009 AQA and its licensors. All rights reserved. klm

6 30 Sequential 31 Sequential 32 Passive Practical skills 33 Practical skills Passive recap of the 555 astable describe the operation and use of a 4017 type counter recognize and draw timing diagrams for the 4017 type counter demonstrate knowledge of gates State and use the fact that a diode conducts in only one direction. know the forward voltage drop is 0.7 V. explain forward and reverse bias display the output of a transformer using an oscilloscope sketch the voltage-time graph for a sine wave measure mains frequency use the relationship peak value = 1.4 rms value explain the use of a diode as a half wave rectifier use oscilloscope. explain the use of diodes in a bridge for a full wave rectifier Construct a circuit using an astable and 4017 with LEDs on some outputs Generate a traffic light sequence using OR gates on the outputs of the 4017 Test a silicon diode and measure the forward voltage drop in a circuit with a battery and lamp. Make oscilloscope measurements using a lab. power supply, Use silicon diodes with a load resistor. Also use LEDs singly and in a bridge with a low frequency signal generator to show which diodes are conducting. Use a higher frequency for display using an oscilloscope. Demonstrate smoothing. (Could also mention voltage regulators but not included in spec.) 34 Basic principles explain the use and applications of a voltage divider calculate the output of a voltage divider assuming negligible load current use the fact that an LDR has a very high resistance in the dark and a low resistance in the light use the fact that a thermistor (ntc type) has a resistance that decreases as it gets warmer take readings of resistance from graphs Set up potential dividers on prototyping board and compare the measured and calculated output values. Use LDRs and thermistors in potential divider circuits and investigate the output. klm Copyright 2009 AQA and its licensors. All rights reserved. 5

7 35 Analogue subsystems Op-amp comparator 36 Analogue subsystems 37 Analogue subsystems Practical skills recall that analogue systems vary with time taking on all values between a minimum and maximum know that an op-amp has a very high input resistance, a low output resistance, a very large voltage gain and saturates at the supply voltage. explain the function and use of a comparator circuit with various sensors know that the op-amp can be used as a one-bit ADC know that a DAC subsystem is required for many applications be aware of the use of low power audio amplifier ICs use the relationship voltage gain (G V = V out /V in ) use a range of measuring instruments oscilloscope and signal generator Build a comparator circuit with a single supply and measure voltage levels. Consider the differences between analogue and digital systems and their relative merits. Build and measure the gain of a low power amplifier using an IC from the spec., a signal generator and an oscilloscope. 38 Analogue subsystems know that the bandwidth is the range of frequencies over which the amplifier produces at least half of its rated power. Measure the bandwidth of the amplifier constructed. 39 System design recap of systems and subsystems Use cards representing the subsystems covered in the spec. to design and explain systems (prelude to controlled assessment) 40 Microcontrollers describe the use and application of microcontrollers know that a microcontroller is a programmable integrated circuit know that software is the list of instructions it follows to carry out different tasks As microcontrollers should not be used in the controlled assessment they should only be seen as an alternative to the subsystems covered in the spec. 41 Revision revise and test Assessment of learning using exam style questions Controlled Assessment 51 Radio systems draw and label the block diagram for a simple radio receiver explain the functions of the subsystems of a simple radio receiver Construct or demonstrate a simple radio receiver (crystal set) 6 Copyright 2009 AQA and its licensors. All rights reserved. klm

8 52 Radio systems explain the meaning of Amplitude and Frequency Modulation. sketch graphs of the carrier wave, signal and modulated waves and relate them to each other. compare the merits of AM and FM explain sensitivity and selectivity 53 System sequence construct and interpret flowcharts Use the many examples from past papers revision for exam 60 final exam klm Copyright 2009 AQA and its licensors. All rights reserved. 7