Hints offered by G Sanderson
Click here to start/reset.
Section 1
Question 1
1a) Hint 1: Think about where the iron is getting its energy from.
1a) Hint 2: What sort of energy makes an iron good at flattening clothes, but dangerous to touch?
1b) Hint 3: The options here are 'open loop' or 'closed loop'. Think about how feedback takes a output value 'back' into a controller - enclosing an area of the diagram.
1c) Hint 4: Remember that a thermistor varies resistance with change in temperature - so its symbol is based on the symbol for a resistor.
Question 2
2a) Hint 1: Power is a RATE of energy use - ie a quantity of energy (in Joules) spread (or divided over) a quantity of time (in seconds) to gives joules/sec or WATTS
Question 3
3a) Hint 1: Think about where the air goes. Main air comes from the manifold, through a valve (usually) but what does it then go on to do?
Question 4
4a) Hint 1: Check the data book for a definition of velocity ratio
4a) Hint 2: Because the driven gear is larger than the driver it will go slower and so the VR should be > 1
4b) Hint 3: Think about the direction in which the teeth of the driver PUSH the teeth of the driven.
Question 5
5a)i) Hint 1: Remember that roads are part of our CIVILisation !
5a)ii) Hint 2: A relatively new branch of engineering that helps to protect our ENVIRONMENT.
5b)i) Hint 3: Social impacts should effect local resident's quality of life.
Question 6
6a) Hint 1: Work your way through the diagram as you work your way through the Boolean expression. Look out for brackets and the requirement of NOT gates.
Question 7
7a) Hint 1: Positive environmental factors should benefit the local wildlife or the global pollution situation.
7a) Hint 2: Negative environmental factors should adversely effect the local wildlife or the global pollution situation.
Section 2
Question 8
8a) Hint 1: Start by combining the two resistors that are in series (by adding them together) - then use the 'Resistors in parallel' formula (from the data book).
8b)i) Hint 2: You have been given the current running through the resistor - so you can use Ohm's law to determine the Voltage.
8b)ii) Hint 3: The voltage that you calculated for part (b)(i) is also the voltage dropping across the series resistors - remember to use their combined value (from part (a))
8b)iii) Hint 4: Currents A1 and A2 will combine to make A3.
8c) Hint 5: The 'impact' can be social, economic or environmental. Please note that you are not been asked to explain the emerging technology.
Question 9
9a) Hint 1: Remember that a systems boundary should be a dashed line that encloses all of the sub-systems, but not the inputs or outputs.
9b) Hint 2: You are asked to describe the control of movement, so you should include the user setting, the control unit, the motor and the positional feedback
9c) Hint 3: Think about which pin acts as a 'signal' and when the transistor is 'on'. Where does current flow?
9c) Hint 4: The pin name 'collector' and the arrow on the emitter pin are clues about which pins current flows between.
9d) Hint 5: Look at where the output is high and define these 2 conditions (in terms of A and B) and then use a Boolean 'Or' (+) to shown that either of these conditions could make the output high.
9e) Hint 6: Work your way down each column of the truth table - being careful of which input is relevant to the function.
Question 10
10a) Hint 1: The four types of motion are linear, circular, reciprocating and oscillating.
10b) Hint 2: Look at the whole circuit and see what conditions are necessary for the cylinder to instroke and then how (and when!) it will outstroke.
10c) Hint 3: For the cylinder to move slowly, air needs to be controlled as it exits the cylinder.
10d) Hint 4: Think about aspects of the circuit that you might want to adjust. Would a microcontroller make this easier?
10e) Hint 5: When instroking, air can not push against the whole of the piston area. Why not? What area do you have to subtract from the piston area?
10e) Hint 6: Check the data book for formulae for effective area and for the force generated by a piston.
Question 11
11a) Hint 1: Remember to use the distance FROM THE PIVOT POINT to where the force is applied when summing the clockwise and anti-clockwise moments.
11a) Hint 2: You could repeat the calculation from part (a)(i) (taking moments around Ra) - however, it will be quicker to use the concept that vertical forces balance.
11b) Hint 3: The term is based around the forces being 'equal'.
11c) Hint 4: You are going to need to re-arrange the equation that involves stress, force and area. You can check this in the data book.
11d) Hint 5: Think about the electrical equipment or systems that a visitor centre would have. Which of these might an electrical engineer have to specify during the design stage?
Question 12
12a) Hint 1: Check the equation for electrical energy in the data booklet - and remember that time is measured in seconds.
12a) Hint 2: Remember that the 'output energy' is always smaller than the input energy - so you will have to multiply your answer from part (a)(i) by 0.64
12b) Hint 3: Energy is lost due to friction as heat and sound. How could these losses be minimised?
12c) Hint 4: Measure the length of line 'F' and then use the scale to calculate the force that this line represents.
12d) Hint 5: You can check the data booklet for the appropriate equation (that you will need to re-arrange) but be careful of the units you use for change in length.
Question 13
13a) Hint 1: Think about how the circuit arrangement might affect the brightness of the lamps and how reliably they illuminate.
13b) Hint 2: The diode allows voltage 'spikes' to dissipate from the transistor's collector pin (the top one) - back to the voltage rail.
13c) Hint 3: Think (and then describe) the order of events as Light goes Up, the LDR's Resistance goes Down - or more usefully the other way round (light decreases)
13d) Hint 4: When the variable resistor's resistance is decreased, the voltage dropping across it will also decrease. But what effect will this have on V in?
13e) Hint 5: Check the data book for the equation that relates the voltage drops and resistances in a voltage divider. Remember that you will need to first determine the voltage across the variable resistor.
13f) Hint 6: Two things to watch out for: both axes use a log scale but remember to also check the units; look out for K values (x1000)
13g) Hint 7: Simulation is done on computer programs - which offers significant advantages. You need to describe two.
Question 14
14a) Hint 1: Economic factors are financial. Think about initial costs and whether the harvest machine will save ongoing costs (such as labour costs).
14b) Hint 2: Both ratios of this compound gear slow down the speed of rotation - so the velocity ratio will be significantly above 1.
Question 15
15a) Hint 1: Work your way step-by-step through the sequence. You can check the shape of the symbols in the data booklet if necessary.
15b) Hint 2: Remember that the buzzer will go on the collector connection to the transistor. Check the output table (on page 36) to see which output pin the buzzer should connect to.