1. Basic Electricity & Electronics Let’s go on a Learning Journey

2. Conductors and Insulators Metals are good conductors because current flows through them easily. Metals are good conductors because current flows through them easily. Wood and most plastics do not allow current to flow and are electrical insulators. Wood and most plastics do not allow current to flow and are electrical insulators. Some materials, such as silicon and germanium, are called semi-conductors because current flows through them, but not as freely as through metals. Some materials, such as silicon and germanium, are called semi-conductors because current flows through them, but not as freely as through metals.

3. A switch with two connections is called a single-pole, single-throw (SPST) switch.A switch with two connections is called a single-pole, single-throw (SPST) switch. A switch with three connections is called a single-pole, double-throw (SPDT) switch.A switch with three connections is called a single-pole, double-throw (SPDT) switch. SWITCHES SPDT

4. A double-pole, double-throw (DPDT) switch has six contacts. DPDT can operate two independent circuits at the same time.A double-pole, double-throw (DPDT) switch has six contacts. DPDT can operate two independent circuits at the same time. SWITCHES DPDT

5. When resistors are connected in series, the combined resistance is higher than the individual resistancesWhen resistors are connected in series, the combined resistance is higher than the individual resistances Worked out by adding each individual value to the next.Worked out by adding each individual value to the next. RESISTORS in series R = R 1 + R 2 R1R1 R2R2

6. When resistors care connected in parallel, the combined resistance is lower than the individual resistances worked out by adding the reciprocal of each individual value to the next.When resistors care connected in parallel, the combined resistance is lower than the individual resistances worked out by adding the reciprocal of each individual value to the next. RESISTORS in parallel R = R 1 + R 2 1 1 1 R1R1 R2R2

7. Resistors reduce the amount of current flowing in a circuit and are used for protecting components from being damaged by too much current.Resistors reduce the amount of current flowing in a circuit and are used for protecting components from being damaged by too much current. They are made in a range of values, with higher values providing a greater resistance.They are made in a range of values, with higher values providing a greater resistance. Resistors can be connected either way round in a circuit.Resistors can be connected either way round in a circuit. Use of RESISTORS

9. RESISTORS Resistors are found in many electronic products a) Draw the symbol of the resistor. b) Describe the purpose of the colour bands found on a resistor. The colour bands are coded to show the values of the resistor c) A gold or silver band is found on the resistor. Explain the purpose. The band shows the accuracy of the resisitor. Gold band for +/- 5% and silver for +/- 10%.

10. A transistor is an automatic switch.A transistor is an automatic switch. Instead of pushing a button or sliding a lever to turn it on or off, it has a contact, called the base, which is used to activate it.Instead of pushing a button or sliding a lever to turn it on or off, it has a contact, called the base, which is used to activate it. BIPOLAR TRANSISTOR

11. Types of SWITCHES Slide switch Tilt switch Reed switch Microswitch Push switch Rotary switch Rocker switch Key switch Membrane panel switch

12. The filament bulb lights up when current passes through.The filament bulb lights up when current passes through. The current causes the filament to become so hot that it glows.The current causes the filament to become so hot that it glows. OUTPUT COMPONENTS

13. Buzzers make a noise when connected to a battery and are often used as warning devices.Buzzers make a noise when connected to a battery and are often used as warning devices. The wires are sometimes coloured coded: red to connect to the positive terminal and black to connect to the negative terminal.The wires are sometimes coloured coded: red to connect to the positive terminal and black to connect to the negative terminal. OUTPUT COMPONENTS

14. Motors are used for turning wheels, pulleys, gears or cams.Motors are used for turning wheels, pulleys, gears or cams. D.C. brush motors having contacts for the battery connection are the most common type.D.C. brush motors having contacts for the battery connection are the most common type. The direction of the spindle rotation can be reversed by swapping the connections at the contacts.The direction of the spindle rotation can be reversed by swapping the connections at the contacts. The larger the motor, the more current it requires.The larger the motor, the more current it requires. OUTPUT COMPONENTS

15. A stepper motor has a permanent magnet rotor that turns inside fixed coils of wire.A stepper motor has a permanent magnet rotor that turns inside fixed coils of wire. The coils are switched on and off in a special sequence to turn the rotor.The coils are switched on and off in a special sequence to turn the rotor. They are precise because the rotors can be made to turn through an exact number of steps.They are precise because the rotors can be made to turn through an exact number of steps. Stepper Motor

16. A solenoid also produces a linear movement.A solenoid also produces a linear movement. It consists of a coil of wire with a plunger in the centre. When the current flows through the coil, it creates a magnetic field, causing the plunger to move through the coil.It consists of a coil of wire with a plunger in the centre. When the current flows through the coil, it creates a magnetic field, causing the plunger to move through the coil. Solenoid

17. A relay is a switch which is operated by a small solenoid.A relay is a switch which is operated by a small solenoid. The relay allows a low voltage circuit called the primary circuit to control a high voltage circuit called the secondary circuit.The relay allows a low voltage circuit called the primary circuit to control a high voltage circuit called the secondary circuit. It also allows high current devices to be switched on and off by a circuit which uses a much smaller current.It also allows high current devices to be switched on and off by a circuit which uses a much smaller current. Relay NC NO

18. A light-emitting diode (LED) glows when a current flows through it.A light-emitting diode (LED) glows when a current flows through it. LEDs are cheap and come in a variety of colours.LEDs are cheap and come in a variety of colours. The leg next to the flat side of the LED is to be connected to the negative terminal of the battery.The leg next to the flat side of the LED is to be connected to the negative terminal of the battery. OUTPUT COMPONENTS anode cathode anode (+) cathode (-) flat side indicates cathode

19. Diodes allow an electric current to flow through in one direction only.Diodes allow an electric current to flow through in one direction only. They are used in circuits for controlling the flow of the current.They are used in circuits for controlling the flow of the current. A standard semiconductor diode does not light up when current flows through it.A standard semiconductor diode does not light up when current flows through it. OUTPUT COMPONENTS anode cathode anode (+) cathode (-)

20. Components and Uses ComponentsApplication and Uses MotorProduces low cost rotary motion that does not required speed control. Used in children’s toys BuzzerFor producing sound. Has built-in signal generator and a pre- designed tone. Used in door bells. BulbThis lights up to give bright light. It is used in torches

21. Components and Uses ComponentsApplication/ Uses Stepper MotorRotary motion with accurate angular position control, accurate speed control by controlling the input frequency SolenoidShort stroke linear motion. Used in electric door latch SpeakerFor producing sound. Requires signal source

22. Components and Uses ComponentsApplication and Uses Cell/ BatterySource of electricity (Direct Current - DC). Used in toys Filament light bulb Lighting. Used in torch light Variable resisitor Provides variable voltage in a voltage divider circuit. Adjust the gain of an amplified circuit ResistorControls or limits the current flowing in a circuit

23. Components and Uses ComponentsApplication and Uses Light- dependent resistor High resistance in the dark, low resistance when exposed to light. Used in automatic light switch circuit. ThermistorHigh resistance when cold, low resistance when hot. Used in temperature heater/ oven control circuit MicrophoneFor picking up sound wave

24. Components and Uses ComponentsApplication and Uses CapacitorSmoothens fluctuating voltage from a rectifier and delay or timing circuit. Used with for electronic differentiation and integration Light-emitting diode (LED) Indicator lights for instrument panel and home appliances. Used Exit sign and in traffic lights.

25. Components and Uses ComponentsApplication and Uses Thyristor (diac) Switches a high power load when triggered by a low power signal. Remains on even when trigger is removed (use in Alarm System) RelaySwitches one or more high power loads when operated by a low signal source

26. Draw a simple electrical (light) circuit to show: (a) its components and (b) its symbols at its switch-off position Include energy source Battery, light bulb and a switch (a) (b)

27. How are components temporary connected in a circuit Components can be temporarily connected using terminal blocks. The plastics covering of the wires must be removed from the ends before they are inserted in the terminal blocks.

28. Bulbs in a Parallel Circuit Bulbs in a Series Circuit

29. Components connected in series and parallel circuit A B C

30. What is a transistor? The transistor is an automatic switch that can be operated by a sensor and has three legs called the base, collector and emitter. Sensor is connected to the base; positive terminal of the battery towards the collector; negative terminal towards the emitter.

31. Draw the transistors and its symbol TransistorsSymbol Positive negative

32. Explain how the input sensor and transistor works? As the sensor detects environmental changes, it causes a voltage change at the base of the transistor.As the sensor detects environmental changes, it causes a voltage change at the base of the transistor. When the voltage rises above 0.6 V, the transistor switches on, allowing current to flow from the collector to the emitter.When the voltage rises above 0.6 V, the transistor switches on, allowing current to flow from the collector to the emitter.

33. What is an open loop system? In an automatic cooling system, when a thermistor (input) senses a rise in the temperature, a propellor blade (output) connected to a motor is turned on by the transistor. When the temperature falls, the transistor switches off. This is an open loop control system because the fan does not actually cool the air. INPUTPROCESSOUTPUT thermistor transistor fan

34. What is a closed loop control system? INPUTPROCESSOUTPUT moisturetransistorwater pump FEEDBACK In an automatic water pump, when a moisture sensor (input) detects water, a water pump (output) operates when the transistor switches the circuit on. When the water level is clear of the sensor, the transistor switches off.In an automatic water pump, when a moisture sensor (input) detects water, a water pump (output) operates when the transistor switches the circuit on. When the water level is clear of the sensor, the transistor switches off.

35. Explain how you can construct a simple transistor circuit to output component to battery transistor copper tape variable resistor to sensor The transistor circuit is easily constructed using self-adhesive copper tape and a soldering iron.The transistor circuit is easily constructed using self-adhesive copper tape and a soldering iron. The tape may be stuck to a small sheet of wood, plastics or card and the components are soldered directly to the tape.The tape may be stuck to a small sheet of wood, plastics or card and the components are soldered directly to the tape. The addition of a variable resistor allows the sensitivity of the circuit to be adjustedThe addition of a variable resistor allows the sensitivity of the circuit to be adjusted

36. A very small current at the base will switch on the transistor, allowing a much larger current to flow between the collector and emitter.A very small current at the base will switch on the transistor, allowing a much larger current to flow between the collector and emitter. BIPOLAR TRANSISTOR

37. The base of a transistor is usually connected to a sensor, such as a light or temperature sensor, which determines the amount of current flowing into the base.The base of a transistor is usually connected to a sensor, such as a light or temperature sensor, which determines the amount of current flowing into the base. When the sensor allows enough current to flow, the transistor switches on.When the sensor allows enough current to flow, the transistor switches on. BIPOLAR TRANSISTOR A resistor is normally connected to the base of a transistor to prevent it from being damaged by too much current.A resistor is normally connected to the base of a transistor to prevent it from being damaged by too much current.

38. In a P-N-P transistor, current is allowed to flow from the emitter to the base and from the emitter to the collector.In a P-N-P transistor, current is allowed to flow from the emitter to the base and from the emitter to the collector. BIPOLAR TRANSISTOR

39. In dry conditions, there is a very high resistance between the contacts of the sensor. No current is able to flow into the base and the transistor is switched off.In dry conditions, there is a very high resistance between the contacts of the sensor. No current is able to flow into the base and the transistor is switched off. SENSORS In dry conditions, no current flows into the base of the transistor so the LED is off.

40. In damp conditions, the resistance between the contacts is much lower. A small current flows into the base and the transistor switches on.In damp conditions, the resistance between the contacts is much lower. A small current flows into the base and the transistor switches on. SENSORS In damp conditions, a small current flows into the base of the transistor so the LED is on.

41. INPUT-PROCESS-OUTPUT diagram for a moisture- sensing circuit.INPUT-PROCESS-OUTPUT diagram for a moisture- sensing circuit. SENSORS INPUTPROCESSOUTPUT probestransistorLED/buzzer

42. Light sensors use a component called a light-dependent resistor (LDR) to determine the amount of current allowed through the circuit when light falls on it.Light sensors use a component called a light-dependent resistor (LDR) to determine the amount of current allowed through the circuit when light falls on it. The LDR is a special kind of resistor which changes its resistance as the light level varies.The LDR is a special kind of resistor which changes its resistance as the light level varies. The LDR is connected to the base of the transistor.The LDR is connected to the base of the transistor. SENSORS

43. In darkness, the LDR has a high resistance (typically 1 M  ), so virtually no current flows through it. The transistor is switched off.In darkness, the LDR has a high resistance (typically 1 M  ), so virtually no current flows through it. The transistor is switched off. SENSORS In dark conditions, no current flows into the base of the transistor so the filament bulb is off.

44. In bright light, the LDR has a low resistance (typically 270  ), allowing a larger current to flow. As the light level increases, the flow of current through the LDR increases, switching on the transistor.In bright light, the LDR has a low resistance (typically 270  ), allowing a larger current to flow. As the light level increases, the flow of current through the LDR increases, switching on the transistor. SENSORS In light conditions, current flows into the base of the transistor so the filament bulb is on.

45. INPUT-PROCESS-OUTPUT diagram for a light-sensing circuit.INPUT-PROCESS-OUTPUT diagram for a light-sensing circuit. SENSORS INPUTPROCESSOUTPUT light- dependent resistor transistorbulb/LED/buzzer

46. The amount of light needed to switch on the transistor in the light-sensing circuit can be adjusted by adding a resistor between the base and negative side of the circuit.The amount of light needed to switch on the transistor in the light-sensing circuit can be adjusted by adding a resistor between the base and negative side of the circuit. The lower the resistor value, the greater the amount of light needed to switch on the transistor.The lower the resistor value, the greater the amount of light needed to switch on the transistor. This arrangement of the LDR and resistor is called a potential divider.This arrangement of the LDR and resistor is called a potential divider. SENSORS

47. To switch on the transistor in dark conditions and off in light conditions, the LDR and the resistor in the potential divider can be reversed by swapping positions.To switch on the transistor in dark conditions and off in light conditions, the LDR and the resistor in the potential divider can be reversed by swapping positions. SENSORS

48. For extra sensitivity, two transistors may be used.For extra sensitivity, two transistors may be used. SENSORS Darlington Pair for extra sensitivity (very small current can pass through

49. Temperature sensors use a component called a thermistor to determine the amount of current allowed through the circuit when temperature changes.Temperature sensors use a component called a thermistor to determine the amount of current allowed through the circuit when temperature changes. The thermistor is a special kind of resistor that changes its resistance as the temperature varies.The thermistor is a special kind of resistor that changes its resistance as the temperature varies. It is connected between the base of the transistor and the positive side of the circuit.It is connected between the base of the transistor and the positive side of the circuit. SENSORS

50. Workings of the type of thermistor that decreases its resistance as the temperature rises is described below and in the next slide.Workings of the type of thermistor that decreases its resistance as the temperature rises is described below and in the next slide. In cold conditions, no current flows through the thermistor so the transistor is switched off.In cold conditions, no current flows through the thermistor so the transistor is switched off. SENSORS

51. As the temperature rises, the flow of current through the thermistor increases, switching on the transistor.As the temperature rises, the flow of current through the thermistor increases, switching on the transistor. SENSORS

52. INPUT-PROCESS-OUTPUT diagram for a temperature- sensing circuit.INPUT-PROCESS-OUTPUT diagram for a temperature- sensing circuit. SENSORS INPUTPROCESSOUTPUT thermistortransistorbulb/LED/buzzer

53. To adjust the sensitivity, a potentiometer may be connected between the base and the negative track.To adjust the sensitivity, a potentiometer may be connected between the base and the negative track. The value printed on a potentiometer states its resistance value between the two outer contacts. By rotating the shaft, the resistance between the middle contact and either of the outer contacts is adjusted.The value printed on a potentiometer states its resistance value between the two outer contacts. By rotating the shaft, the resistance between the middle contact and either of the outer contacts is adjusted. SENSORS

54. For extra sensitivity, two transistors may be used.For extra sensitivity, two transistors may be used. SENSORS

55. An electrolytic (polarised) capacitor must be connected so that the leg marked with an arrow or ‘-’ sign is connected to the negative side of the circuit.An electrolytic (polarised) capacitor must be connected so that the leg marked with an arrow or ‘-’ sign is connected to the negative side of the circuit. Electrolytic (polarised / +ve; -ve) Capacitor

56. non-electrolytic (non-polarised) capacitor A non-electrolytic capacitor (non-polarised) can be connected either way around.A non-electrolytic capacitor (non-polarised) can be connected either way around.