BE8255 BASIC ELECTRICAL, ELECTRONICS AND MEASUREMENT ENGINEERING UNIT I

1. BE8255 -BASIC ELECTRICAL, ELECTRONICS AND MEASUREMENT ENGINEERINGByN. Rajagopalakrishnan, AP/ECE

2. BE8255 BASIC ELECTRICAL, ELECTRONICS AND MEASUREMENT ENGINEERING UNIT I ELECTRICAL CIRCUITS ANALYSIS Ohms Law, Kirchhoff‘s Law-Instantaneous power- series and parallel circuit analysis with resistive, capacitive and inductive network - nodal analysis, mesh analysis- network theorems - Thevenins theorem, Norton theorem, maximum power transfer theorem and superposition theorem, three phase supply-Instantaneous, Reactive and apparent power-star delta conversion.

3. Electric Current • Electric current is the continuous flow of electric charge • Two types of current are direct and alternating • Direct current (DC) is when the charge flows in one direction • Alternating current (AC) is when the flow of electric charge regularly reverses direction

4. Electric Current • An example of a direct current is a flashlight and most battery-operated devices • Alternating current is in your home and school • Current is defined as the direction in which the positive charges would flow

5. Conductors and Insulators • An electrical conductor is a material through which charge can flow easily • Metals such as copper, and silver are good electrical conductors • An electrical insulator is a material through which charge cannot flow easily • Wood, plastic, rubber and air are good electrical insulators

6. Resistance • Resistance is the opposition to the flow of charges in a material • The SI unit of resistance is the ohm • A material’s thickness, length and temperature affect its resistance • Resistance is more in a longer wire • As temperature increases the resistance increases since the electrons collide more often

7. Resistance A superconductor is a material that has almost zero resistance when it is cooled to low temperatures Superconductors are trying to reduce the resistance to zero The best superconductor has been cooled to 138K

8. Voltage • In order for a charge to flow in a conducting wire, the wire must be connected in a complete loop that includes a source of electrical energy • A flashlight will not work if there is no battery

9. Potential Difference • Reminder potential energy is related to position • Charges flow from a high to low potential energy • Potential difference is the difference in electrical potential energy between two places in an electric field

10. Voltage Sources • Three common voltage sources are batteries, solar cells and generators • A battery is a device that converts chemical energy to electrical energy • In a 9-volt battery the voltage drop is about 9 volts

11. Electricity Physical phenomenon arising from the existence and interactions of electric charge

12. Charge Characteristic property of subatomic particles responsible for electric phenomena Charge is the source of one of the fundamental forces in nature (others?) + - Proton Electron −1.602×10−19 C 1.602×10−19 C The unit of electric charge is coloumb (C) 1 coloumb = 6.25 × 1018 e e = elementary charge = charge of proton

13. Charge “Charged” particles exhibit forces - - Like charges repel each other + - Opposite charges attract one another

14. ATOMS AND ATOMIC STRUCTUREAtom Nucleus Proton Neutron Electron

15. WHAT IS AN ATOM? • The smallest unit of an element. • Consists of a central nucleus surrounded by one or more electrons.

16. WHAT IS THE NUCLEUS? • The central part of an atom. • Composed of protons and neutrons. • Contains most of an atom's mass.

17. WHAT IS A PROTON? • Positively charged particle. • Found within an atomic nucleus.

18. WHAT IS A NEUTRON? • Uncharged particle. • Found within an atomic nucleus.

19. WHAT IS AN ELECTRON? • Negatively charged particle. • Located in shells that surround an atom's nucleus.

20. Electric current Moving electrons in a conductive material or moving ions IS called Current Describes charge in motion, the flow of charge is called current

21. Electric current An ampere (A) is the number of electrons having a total charge of 1 C moving through a given cross section in 1 s. As defined, current flows in direction of positive charge flow

22. Current • Symbol: I • Unit: Ampere

23. Current-Water Analogy

24. Voltage • Symbol: V • Unit: Volt • Potential difference across two terminals in a circuit “across variable.” • In order to move charge from point A to point B, work needs to be done. B A

25. Voltage-Water Analogy

26. NODES, BRANCHES, AND LOOPS: A branch: A branch is a single electrical element or device.      Figure 4.1: A circuit with 5 branches. A node: A node can be defined as a connection point between two or more branches.    Figure 4.2: A circuit with 3 nodes. 2

27. Branch A branch is any portion of a circuit with two terminals connected to it. A branch may consist of one or more circuit elements. In practice, any circuit element with two terminals connected to it is a branch. Definition of a branch

28. NodeA node is the junction of two or more branches (one often refers to the junction of only two branches as a trivial node). The figure below illustrates the concept. Definitions of node and supernode

29. Loop A loop is any closed connection of branches. Various loop configurations are illustrated below. Definition of a loop

30. Mesh A mesh is a loop that does not contain other loops. Definition of a mesh

31. Series Connection of Cells • Each cell provides 1.5 V • Two cells connected one after another, inseries, provide 3 V, while three cells would provide 4.5 V • Polarities matter

32. Parallel Connection of Cells • If the cells are connected in parallel, the voltage stays at 1.5 V, but now a larger current can be drawn.

33. Wire-Water Analogy

34. Resistor Concept —I • Flow of electric current through a conductor experiences a certain amount of resistance. • The resistance, expressed in ohms (W, named after George ohm), kilo-ohms (kW, 1000W), or mega-ohms (MW, 106W) is a measure of how much a resistor resists the flow of electricity. • The magnitude of resistance is dictated by electric properties of the material and material geometry. • This behavior of materials is often used to control/limit electric current flow in circuits. • Henceforth, the conductors that exhibit the property of resisting current flow are called resistors. Resistor Symbols

35. Resistor Applications • Resistors are used for: • Limiting current in electric circuits. • Lowering voltage levels in electric circuits (using voltage divider). • As current provider. • As a sensor (e.g., photoresistor detects light condition, thermistor detects temperature condition, strain gauge detects load condition, etc.) • In electronic circuits, resistors are used as pull-up and pull-down elements to avoid floating signal levels.

36. Wire-wound resistors have a label indicating resistance and power ratings. A majority of resistors have color bars to indicate their resistance magnitude. There are usually 4 to 6 bands of color on a resistor. As shown in the figure below, the right most color bar indicates the resistor reliability, however, some resistor use this bar to indicate the tolerance. The color bar immediately left to the tolerance bar (C), indicates the multipliers (in tens). To the left of the multiplier bar are the digits, starting from the last digit to the first digit. Resistor value = Resistor Labels

37. Resistor Color Codes Band color Digit Multiplier Black 0 X1 Brown 1 X10 Color Tolerance Red 2 X100 Brown ±1% Orange 3 X1000 Yellow 4 X10000 Red ±2% Green 5 X100000 Gold ±5% Blue 6 X1000000 violet 7 X10000000 Silver ±10% Grey 8 X100000000 None ±20% White 9 X1000000000 Silver - x.01 Gold - x.1

38. Example • The first band is yellow, so the first digit is 4 • The second band is violet, so the second digit is 7 • The third band is red, so the multiplier is • Resistor value is

39. Metric Units and Conversions Abbreviation Means Multiply unit by Or p pico .000000000001 10 -12 n nano .000000001 10 -9 µ micro .000001 10 -6 m milli .001 10 -3 . Unit 1 10 0 k kilo 1,000 10 3 M mega 1,000,000 10 6 G giga 1,000,000,000 10 9

40. DigitalMultimeter 1 • DMM is a measuring instrument • An ammeter measures current • A voltmeter measures the potential difference (voltage) between two points • An ohmmeter measures resistance • A multimeter combines these functions, and possibly some additional ones as well, into a single instrument

41. AmmeterConnection • Break the circuit so that the ammeter can be connected in series • All the current flowing in the circuit must pass through the ammeter • An ammeter must have a very LOW input impedance

42. VoltmeterConnection • The voltmeter is connected in parallel between two points of circuit • A voltmeter should have a very HIGH input impedance

43. OhmmeterConnection • An ohmmeter does not function with a circuit connected to a power supply • Must take it out of the circuit altogether and test it separately

44. Resistors in Series Rtotal=R1+R2 Rtotal=1+1=2kΩ

45. Resistors in Parallel

46. Exercise 1

47. Capacitor Concept • A capacitor is an energy storage element which is analogous to the spring element of mechanical systems. • It can store electrical pressure (voltage) for periods of time. • -When a capacitor has a difference in voltage (electrical pressure) across its plate, it is said to be charged. • -A capacitor is charged by having a one-way current flow through it for a period of time. • -It can be discharged by letting a current flow in the opposite direction out of the capacitor.

48. +q: positive charge gain due to electrons lost Direction of electron displacement +q: negative charge gained due to electrons gained Capacitor Construction • A capacitor is constructed using a pair of parallel conducting plates separated by an insulating material (dielectric). • When the two plates of a capacitor are connected to a voltage source as shown, charges are displaced from one side of the capacitor to the other side, thereby establishing an electric field. • The charges continue to be displaced in this manner until the potential difference across the two plates is equal to the potential of voltage source.

49. Pipe filled with water Rubber diaphragm sealing center of pipe Plunger Capacitor Water Pipe Analogy —I • In the water pipe analogy, a capacitor is thought of as a water pipe: • with a rubber diaphragm sealing off each side of the pipe and • a plunger on one end. • When the plunger pushes toward the diaphragm, the water in the pipe forces the diaphragm to stretch until the force of the diaphragm pushing back on the water equals the force on the plungerpipe is charged! • If the plunger is released, the diaphragm will push the plunger back to its original position pipe is discharged.

50. + Variable capacitor Fixed capacitor Polarized capacitor Capacitor Symbols