2 Grading policy Participation 10 marks HWs 10 marks Quizzes 10 marks Preparation, Promptness, Level of Engagement, BehaviorHWs marks2 HWsQuizzes marks2 quizzes & SWQPractical marksLab activities and Practical examIAT competency exams (practical and knowledge ) marks
3 Preparation marksPrint the modules and cover it and bring it to every class with youCalculatorStationaryLab cout
4 Participation Marks Promptness: On time or Late Level of Engagement Behavior
5 Objectives Electrical Circuit Components Power supplies Types of power suppliesFunctions of power suppliesClose circuit / open circuitSwitchesPartsManually operated switches: Knife Switch, push button and selector switch
6 Electrical Circuit Components How many elements do you see ?Input device, what do you think it do?Output device / Load. Give example of other loadsHow the elements are connected ?What does generate the electric current ?Which device allow the current to flow ?
7 Power suppliesPower supply are used in electrical systems to modify the power supplied from the power company (e.g. from the wall socket) to a form that is needed for the application.One feature power supplies are usually designed to do, is provide a constant current or constant voltage output. This is called regulation.
8 Application: Widely used Power Supplyconstant currentpower supplythe same current level regardlessof the demand placed on it by the load. However, the voltage variesaccording to the size of the load.Application: Limitedconstant voltage power suppliesThey maintain a constant voltage output, regardless of the load.Here, the current varies instead of the voltage.Application: Widely used
9 Constant voltage power supply DC VoltageAC voltageFunction Generator
11 DC Power Supply, Battery A battery depends on chemical reaction to produce electricity. It does not require an external source of power.However, most constant voltage supplies, require an external AC power source.
12 Functions of Power supplies Regulating voltage or current (providing constant voltage or constant current)Reducing voltage levelsChanging AC to DCProviding over current protection.
23 Class warm up Electrical Circuit Components Power supplies Types of power suppliesFunctions of power suppliesClose circuit / open circuitSwitchesPartsManually operated switches: Knife Switch, push button and selector switch
24 Objectives Lab activity 2, testing different kinds of switches Output devices
29 LampA lamp contains a resistive element inside a glass bulb. The bulb is filled with a gas. When current flows through the element, the element heats up and excites the gas. This produces the light that we see
30 Resistor A resistor limits the flow of electrical current. It is one of the most commonly used components in an electrical circuit.Resistors are often used with motors to suppress the surge of current and allow the current to the motor to be gradually increased.A resistor is made of a material that does not allow current to easily flow through ex. carbon.
31 BuzzerWhen electricity is applied to a buzzer, it causes a vibration to occur inside the buzzer’s housing. This vibration is what causes the buzzing noise.
32 SolenoidA solenoid produces linear mechanical motion from electrical energy.Solenoids are used tooperate flippers in pinball machinesoperate fluid power valvesturn motors on and off
33 Solenoid Solenoid consist of armature (plunger)C Frame (coil)The solenoid has an armature or plunger that moves in a linear motion when electrical current is applied to its electrical coil
34 MotorA motor is the output device that produces rotary mechanical motion, ex. a fan
38 High current High current can damage electrical components. High current occur for two reasons:many loads are connected to the circuitA short circuit
39 Short circuitA short circuit is a direct path with little or no resistance created between the positive and negative terminals of the power supplySince current flows through the path with least resistance, it will take this path.
41 Circuit protectionDevices used to protect electrical components from high current:FuseCircuit Breaker
42 The Fuse OperationA fuse is used to protect the circuit components from high current.The fuse must be replaced each time an overload or short circuit condition occurs.Fuses are used in applications where a problem rarely occurs, ex. car’s light
43 What is the current ratings for the following fuses ? Fuses are rated for a maximum current value.If the maximum current value is exceeded, the fuse blows to protect the components of the circuit.What is the current ratings for the following fuses ?
44 Fuse ratingWhen the current flow exceeds the rated value of the fuse, the wire or foil strip melts and opens the circuit (the fuse is blown).
45 Testing the continuity of the fuse If the fuse is good, it has continuity (like a wire)If a fuse is blown, it has no continuity.
46 Say it in a simple words… FusesMany electrical devices have fuses.Fuses are easy to replace.Fuse are low cost. One fuse cost 0.25 DHS per fuse.Special care needs to be taken to make sure that the properly rated fuse is installed to provide the needed protection.Say it in a simple words…
47 Circuit BreakersCircuit breaker is used to protect the circuit components from high current.Just as a fuse blows, a circuit breaker opens or trips when an excessive current is present.The circuit breaker can be reset and used again.
48 Circuit breakers are used where overloads commonly occur Ex. power supply and your house wiring
49 Testing the continuity of the circuit breaker If the breaker is tripped, it has no continuityif the breaker is reset, it has continuity
50 Circuit breaker Circuit breakers are either thermally-triggeredtripped due to heat caused by excessive currentmagnetically-triggeredtripped due to the strength of the magnetic field created by excessive current.In some cases a circuit breaker is combination of both
51 Circuit breakers can have different types of reset switches Some have lever type resets, while some have pushbutton resets.Most newer homes and businesses use circuit breakers in their electrical control pannelcontrol panels electrical control panels.
52 Is it lever type or push button type? When this circuit breaker will trip?
53 Activity 4I=24/25 = 0.96 AI= 1.25 AWait for about 30 seconds to see if the circuit breaker “trips” off.Repeat step 2 and observe the circuit breaker’s operation.I=24/10 = 2.4 A
54 Activity 4 Measure continuity of the circuit breaker Replace the 10 ohm resistor with a 25 ohm resistor.
55 Recap High current Short circuit Circuit protection: Fuse and circuit breakerFuse ratingFuse operationTesting the continuity of the fuseCircuit breaker