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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.

Did this hint help?