Electrical systems

Electronic systems

Name: __________________________________________________

Power supplies

1. What is mains electricity?

2. What are the two main properties of mains electricity?

What are nominal values of these in Europe?

3. Mains power is described as a.c. What does a.c. stand for? _______________________________________

4. Draw a graph on the axes below to show a waveform that represents mains voltage. Label the axes and the

waveform. Explain what a cycle is.

5. List some standard battery sizes and state their nominal voltage.

6. There are several different types of battery. List some of the types, describe them and state typical uses.

Cycle

7. What is d.c. when referring to voltage supplies? Draw the graph of a typical d.c. supply.

8. What is “battery capacity”?

9. What is the capacity of a battery that can supply 2 amps for 4 hours?

How long can a 10 Ah battery supply 2 A of electricity?

How long can a 4 Ah battery supply 8 A of electricity?

Basic components

10. What is the function of a resistor?

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11. Draw the symbol for a resistor?

12. What is the unit of resistance? ______________________________

13. Use the resistor colour code to work out the value of these resistors.

Orange White Red ____________

Red Violet Brown ____________

Brown Green Black ____________

Green Blue Orange ____________

Red Red Red ____________

Yellow Violet Yellow ____________

Green Black Orange ____________

Red Red Orange ____________

Grey Red Brown ____________

Brown Green Orange ____________

14. What are the values of these resistors?

5600 Ohms ____________

150 Ohms ____________

82 Ohms ____________

47000 Ohms ____________

3300 Ohms ____________

220 Ohms ____________

18 Ohms ____________

18000 Ohms ____________

120000 Ohms ____________

2700 Ohms ____________

15. Draw diagrams to show resistors connected:

a) in series b) in parallel

16. Explain, with the aid of a diagram, how a variable resistor can be used to control current and voltage.

17. Write the formula for Ohm’s law, including the units used for each term.

18. a) Bicycles with battery operated lights often have different size bulbs for the front and rear lights. The filament

in the front lamp has a resistance of 3 ohms. It takes a current of 0.6A. What voltage does it work at?

Show all lines of working.

b) A 120 ohm resistor is connected to an LED and has 0.1 amps flowing through it. What is the voltage dropped

across the resistor?

c) A 9 volt battery supplies a current of 0.2 amps in a lighting circuit. What is the resistance of the lamp in the

circuit?

19. What is the function of a capacitor?

20. What are the units of capacitance?

21. Draw the symbol for:

a) a polarised (electrolytic) capacitor b) a non-polarised capacitor

22. What is a milli Farad? _____________________________________________________________________

Write these values as milli Farads:

a) 0.001F b) 0.02F c) 0.5F

d) 0.003F e) 0.047F f) 0.1F

23. What is a micro Farad? ____________________________________________________________________

Write these values as micro Farads:

a) 0.000001F b) 0.00002F c) 0.0005F

d) 0.00003F e) 0.00047F f) 0.0001F

24. Draw charging and discharging graphs for a capacitor.

25. What is the function of a diode?

26. What is a signal diode typically used for?

27. What is a rectifier diode typically used for?

28. Explain half wave rectification.

29. Explain full wave rectification and how it differs from half wave rectification.

30. How is a rectified signal ‘smoothed’ to convert the ‘rippled’ output to a more smooth dc output voltage.

Systems

31. Systems are designed initially by drawing a block diagram. Label each block in the diagram below.

32. Each block can perform different functions, depending on the system design. Make a list of possible functions

below.

33. What is the function of an input device?

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34. Name the input devices shown below and state their function.

Name: __________________

Function:

Name: __________________

Function:

Name: __________________

Function:

35. Explain the function of an LDR and a thermistor, using graphs to help explain their function.

LDR Thermistor

36. There are many different types of switch. Name the examples shown below.

Name: __________________ Name: __________________ Name: __________________

37. What do these symbols represent?

38. Some input devices are analogue and will produce an analogue signal. Explain what an analogue signal is and

draw an example on the axes below.

Explanation: ________________________________

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39. Some devices produce a digital signal. Explain what a digital signal is and draw an example on the axes below.

Label the high and low parts of the signal.

Explanation: ________________________________

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40. Some process blocks of a system will only work with digital inputs. If an analogue input is used then an analogue

to digital converter (ADC) is needed. Use the diagram below to help explain what happens in analogue to digital

signal conversion.

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41. To which part of the system diagram does a timer belong?

42. What type of IC package is a 555 timer housed in?

43. Label the pins on the IC package shown here.

How can you easily identify pin 1?

44. A typical 555 astable circuit diagram is shown.

Explain what happens at the output of the circuit.

45. Draw and label a graph showing the output from an astable circuit.

46. A typical 555 monostable circuit is shown here.

Explain the function of the circuit.

47. Draw and label a graph showing the output from a monostable circuit

48. Counters are very popular process devices in electronic products. Name a few typical applications.

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49. A decade counter is an example of a type of counting device. Explain what a decade counter is.

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50. Using the circuit diagram (schematic) as reference, explain how the system is made to count and what the

counting will look like.

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51. What is a comparator?

52. What type of device is often used to create a comparator circuit? Draw its symbol.

53. Use the circuit diagrams below to help explain how the comparator circuit works.

54. Name three logic gates and draw their symbols. Give a brief explanation of the function of each one and draw

diagrams to help explain their function.

Name

Symbol

Function

Name

Symbol

Function

Name

Symbol

Function

55. What is a microcontroller?

56. One type of microcontroller is called a PIC. What is a PIC?

57. In what types of product might you find a microcontroller?

58. State some advantages of using a microcontroller in a system.

59. State some disadvantages of using a microcontroller in a system.

60. Produce a flowchart for a microcontroller that will carry out the following functions:

It detects when a switch has been pressed

It will turn on a buzzer for five seconds and then turn it off

It will flash a set of LEDs for ten seconds, with a frequency of 2Hz

61. What is interfacing and why are ‘drivers’ required at the output of some systems?

62. Transistors are devices that can be used to interface different blocks in a system. Name two types of transistor

and draw their symbols, labelling each leg.

Name: _____________________ Symbol:

Name: _____________________ Symbol:

63. What are transistors used for?

64. Name the light output devices shown below and draw their symbols.

Name: __________________

Symbol:

Name: __________________

Function:

Name: __________________

Function:

65. Name the sound output devices shown below and draw their symbols.

Name: __________________

Symbol:

Name: __________________

Function:

Name: __________________

Function:

66. What is a solenoid and how does it work?

67. Draw the symbol for a relay.

68. With the aid of the diagram below explain how a relay works.

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69. Explain what is happening in this circuit.

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70.

Analyse the alarm system and give two operating requirements for the alarm control system.

Explain the reason why each requirement is important.

An example of how to answer is given.

Requirement: The alarm should remain armed until the correct code is entered on a keypad, or a swipe card is

presented.

Reason: To prevent unauthorised access to the building.

Requirement 1 ______________________________________________________________________________

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Reason 1 ___________________________________________________________________________________

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Requirement 2 ______________________________________________________________________________

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Reason 2 ___________________________________________________________________________________

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