Circuits. What are circuits?

Transcription

1 Circuits

2 Circuits What are circuits? A closed loop made of a conducting substance that allows electrons to flow from the negative terminal to the positive terminal

3 Parts of a Circuit 1 Power Supply Provides the push needed by the electrons to travel through the circuit Has positive and negative terminals Examples: batteries, generators, outlet, etc.

4 Parts of a Circuit 2 Wires Used to connect the various components of the circuit These form the main path used by the electrons

5 Parts of a Circuit 3 Control Used to control how the electrons flow in the circuit E.g. switch

6 Parts of a Circuit 4 Fuses and Breakers Used to protect the circuit and those using it! They act by breaking (opening) the circuit and thereby stopping the flow of electrons when there is too much demand on the circuit

7 Parts of a Circuit 4 Fuses and Breakers Fuse: Contains conductive filament that melts if current exceeds certain level Breakers: Strip bends when current exceeds a certain level and opens the circuit

8 Parts of a Circuit Fuse Circuit Breaker

9 Parts of a Circuit 5 Transformers Devices used to transfer electrical energy from one circuit to another OR to transform electrical energy into another type of energy (sound, light, mechanical, etc) Ex: motor, light bulb, speakers, etc

10 Parts of a Circuit 5 Resistors Used to slow down or even stop the flow of electrons in a circuit

11 Parts of a Circuit - Symbols Wires Battery Fuse Power supply Switch Motor Light bulb Resistor Ammeter & Voltmeter

12 Electric Circuit Closed path along which electrons from a power source can flow. Light Circuit diagram Graphical representation of an electric circuit. L1 Resistor V s R1 Switch SW1

13 Example I: Analyzing a Circuit L1 V s SW1 OPEN OFF OFF L2 CLOSED ON ON

14 Example I: Analyzing a Circuit L1 V s SW1 OPEN OFF OFF L2 CLOSED ON ON

15 Example I: Analyzing a Circuit L1 V s SW1 OPEN OFF OFF L2 CLOSED ON ON

16 Example II:

17 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

18 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

19 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

20 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

21 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

22 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

23 Example II: Analyzing a Circuit L1 L2 SW1 OPEN OPEN OFF OFF OPEN CLOSED OFF ON SW2 CLOSED OPEN OFF OFF CLOSED CLOSED ON ON V s

24 Types of circuits Series All elements connected in a row Only one pathway for the electrons to take Parallel Multiple pathways for the electrons to take

25 Notice how they drew the current going + to - Draw the circuit diagrams for these two circuits! DON T DO THAT!

26 Series or Parallel? Parallel

27 Recall Ammeters are always connected in line with the components (in series) Voltmeters are always connected across two points (in parallel)

28 Example: A Ammeter To measure the current, the ammeter must be installed into the circuit so that the electrons pass through it. _ +

29 Example: In order to measure the potential difference across a component, the voltmeter must be connected to each side of the component. + V _

30 Example: + _ V If we wish to measure the potential difference across the light

31 Past Exam Questions A mystery circuit consists of two light bulbs (L 1 and L 2 ), a switch, and a power supply. The following table shows what happens to both light bulbs when the switch is opened or closed. Test Open the switch Close the switch Observations L 1 stays on L 2 goes out L 1 stays on L 2 comes on

32 Which diagram correctly represents this mystery circuit? A) C) B) D)

33 Past Exam Questions The electrical circuit of a magnetic alarm system is illustrated in the diagram below.

34 Which of the following shows the correct match between the five numbered components in this circuit diagram and their corresponding electrical functions? Switch Wire Alarm (sound) Battery Fuse? A control conduction transformation Power supply protection B control conduction Power supply transformation protection C D power supply power supply protection transformation control conduction conduction protection transformation control

35 Past Exam Questions When a grocery store check-out clerk is ready to serve customers: - he must press a switch to turn on a light indicating that the cash is open - he can start the conveyer belt motor, if necessary, by using another switch - he can start the conveyer belt motor only if the light is on to indicate that his cash is open

36 Which electrical circuit represents the situation described above? he must press a switch to turn on a light indicating that the cash is open he can start the conveyer belt motor, if necessary, by using another switch he can start the conveyer belt motor only if the light is on to indicate that his cash is open