Electric vs Electronic

1
Electric vs Electronic

• Electric
• usually refers to significant power levels
• produce heat, light, motion
• Electronic
• usually refers to small power levels
• contain semiconductors (transistors and
  integrated circuits), electron tubes, CRT's

2
Electric Circuit

• Source
• Switch
• Components
• Connections

3
DC versus AC

• Electron flow in one direction
• Battery
• Rectified AC

• Electrons alternate direction
• Most common in electrical delivery
• Easiest to generate

4
Voltage

• Potential Difference
• Electromotive force
• Difference in charge

5
Resistance

• The property of a conductor that limits or
  restricts current

6
Ohms Law

• V I x R I V / R R V / I
• V
• ________________
• I x R

7
Ohms Law

• The relationship between current (I), voltage
  (V), and resistance (R)

8
Using Ohms Law

• 1. Given a current of 4 amps and resistance of
  250 Ohms, what is the expected voltage?

9
Using Ohms Law

• 2. Given a voltage of 120 VAC and a resistance of
  3 kOhms, what is the expected current?

10
Using Ohms Law

• 3 Given a voltage of 12 VDC and a current of 0.4
  amps, what resistance is present?

11
Calculating Power

• Power is the product of current and voltage
• P I x V
• Substituting using Ohms Law
• P I x I x R I2 x R
• P ( V / R ) X V V2 / R

12
Electrical Power

• Power is Energy (Work) per unit time
• Electrical power is measured in watts
• Kilowatts are like horsepower
• Approximately 746 W 0.746 KW 1 HP
• Kilowatts are a measure of how much energy is
  flowing in a circuit in a period of time

13
Calculating Power

• a. How much resistance does the filament of a 100
  watt light bulb have when lit?
• b. How much current flows through a 100 watt
  light bulb?
• c. How much power is dissipated if 5 volts are
  placed across a 10 kOhm resistor?

14
Electrical Power Utilities

• True or False
• Electric utilities charge their customers for
  power (kilowatts) used
• What are kilowatt-hours (kwh) a measure of?

15
Equation Summary
16
Alternating Current

• Varies with Time
• Magnitude
• Polarity
• Direction of Electron Flow
• Usually Sinusoidal
• Could be Triangular
• Square
• Mixed Mode

17
Sinusoidal Waveforms

• Period
• The Amount of Time to Complete One Cycle
• Frequency
• How Many Cycles in a Particular Time
• Usually, cycles per second (hertz)
• Frequency is 1 / period

18
Sinusoidal Waveforms
19
Sinusoidal Waveforms

• Peak Value (Maximum and Minimum)
• Positive and Negative
• One-Half of Total Voltage or Current Variation
• Peak to Peak
• Total Change in Voltage or Current

20
Waveforms

• rms Value
• dc voltage that would produce the same effect
• average power value with time
• Sine Wave
• rms 0.707 x Peak
• Square Wave - rms Peak
• Triangular - rms 0.5 x Peak

21
Waveforms

• 110 VAC - rms or Peak ?
• 12 VDC - rms or Peak ?
• Average Voltage - Not Used

22
Safety
23
Series and Parallel

• Example worked in Class
• Illustrate that ground is relative

24
Power Supply schematic

• Explain power supply schematic

25
Series, Parallel, Series-Parallel (Review)
26
Series Resistance

• The simplest form of a circuit
• Resistors connected
• Tool for analyzing circuits
• Equivalent total resistance(Total)
• Current in a series circuit is
• Supply voltage / Equiv. resistance

27
Ohms Law for Series

• Assume a voltage supply of 10v
• Assume three resistors in series
• 200ohms, 500ohms, 300ohms
• Calculate the current

28
Ohms Law for Series

• For the circuit, I V / R
• R Requiv Sum of series R(s)
• Requiv R1 R2 R3
• Requiv 200 500 300 1000ohms
• I 10 / 1000 0.01 Amps

29
Ohms Law for Series

• Analyze the circuit further
• What is the voltage drop across each resistor?
• For a series circuit
• Current is the same throughout the circuit
• Current through each resistor is 0.01 Amps

30
Ohms Law for Series

• Voltage across R1
• V1 I x R1 0.01 x 200 2v
• Voltage across R2
• V2 I x R2 0.01 x 500 5v
• Voltage across R3
• V3 I x R3 0.01 x 300 3v
• CHECK
• Vtotal 253 10v (Supply)

31
Ohms Law for Series

• What is the Voltage (Absolute) between Resistors?
• After R1 Vs - V1
• 10 - 2 8v
• After R2 Vs - V1 - V2
• 10 - 2 - 5 3v
• After R3 Vs - V1 - V2 - V3
• 10 - 2 - 5 - 3 0 (Ground)

32
Ohms Law for Series

• Determine equivalent resistance
• Calculate Current
• Find voltage drops for each R
• Find voltage level between resistors

33
Application of Series

• Given a supply of 12v, provide a 9v and a 6v
  supply
• Using voltage divider concept
• What resistance conbination will produce 9v and
  6v
• Common denominator is 3v
• 3v is one fourth of 12v

34
Application of Series

• Selecting 400ohms as the total resistance
• Dividing it using four 100ohms resistors
• I 12v / 400 0.03 Amps
• V1 0.03 x R1 0.03 x 100 3v
• V2 V3 V4 V1 3v

35
Voltage Division
36
Application of Series

• Voltage after R1 is
• Vs - V1 12 - 3 9v (desired value)
• Voltage after R2 is
• Vs - V1 - V2 12 - 3 - 3 6v (desired value)
• CIRCUIT IS CALLED A VOLTAGE DIVIDER CIRCUIT

37
Power in a Series Circuit

• P I x V
• Overall P I x Vs
• Individually, P1 I x V1
• Ptotal P1 P2 P...

38
Ground

• Can be anywhere in a circuit
• Establish reference plane
• REMEMBER
• Voltage is relative

39
Open/Short Circuit

• Voltage is present at an open circuit
• Disconnect
• Short circuit has zero resistance
• High current
• Limited by fuses

40
Ohms Law and Parallel

• Assume a voltage supply of 10v
• Assume two resistors in parallel
• 250ohms, 500ohms
• Calculate the current

41
Ohms Law and Parallel

• For the circuit, I V / R
• In a parallel circuit, each resistor provides an
  alternative path
• Hydraulic analogy

42
Ohms Law for Parallel

• R Requiv
• Requiv 1 / (1/R1 1/R2 )
• Requiv 1 / ( 1/250 1/500 ) 167ohms
• Isupply 10 / 167 0.06 Amps

43
Ohms Law for Parallel

• Analyze the circuit further
• What is the voltage drop across each resistor?
• For a parallel circuit
• Voltage is the same across each resistor (10
  Volts)
• Current (electrons) divide

44
Ohms Law for Parallel

• I V / R
• I1 V / R1 10 / 250 0.4 amps
• I2 V / R2 10 / 500 0.2 amps
• CHECK
• I1 I2 0.4 0.2 0.6a Isupply
• CURRENT DIVIDER

45
Current Division
46
Applications of Parallel

• House wiring
• Allows separate fuse protection
• Factories
• Distribution of power
• Power supplies in machinery
• Indicator lights

47
Power in Parallel

• Power for each component is P I x V
• Ptotal P1 P2 V ( I1 I2) 10 ( .2 .4 )
  6 watts Psupply

48
Open/Short Circuits

• An open in a parallel leg acts like infinite
  resistance
• No current flows
• Current division is upset
• Short circuit acts like zero R
• All current would bypass other legs
• Must be protected by fuse

49
Identify series-parallel

• A series followed by two in parallel

50
Identify series-parallel

• More challenging series-parallel

51
Identify series-parallel

• Series - Parallel - Series

52
Identify series-parallel

• Parallel - Parallel

53
Analyze series-parallel

• Find the equivalent resistance for the parallel
  section(s)
• Find the total resistance for the circuit
• Calculate the current
• Calculate the voltage at each node

54
Analyze series-parallel

• Compute the Parallel R-equivalent

55
Analyze series-parallel

• Requiv 1/(1/8K) (1/10K) 4.44K

56
Analyze series-parallel

• Circuit Rtotal 5K 4.44K 9.44K

57
Analyze series-parallel

• Current I V/Rtotal20/9.44k2.12mA

58
Analyze series-parallel

• Voltage drop across R1 IxR1 2.12ma x 5K
  10.6 V

59
Analyze series-parallel

• Voltage at B 20 - 10.6 9.4 V

60
Analyze series-parallel

• Voltage drop R2 Voltage drop R3

61
Analyze series-parallel

• I2 V2 / R2 9.4 / 8K 1.18 mA

62
Analyze series-parallel

• I3 V3 / R3 9.4 / 10K 0.94 mA

63
Analyze series-parallel

• Requiv
• Rtotal
• I-total
• Voltages

64
Analyze series-parallel

• Requiv
• Rtotal
• I-total
• Voltages

65
Analyze series-parallel

• Requiv
• Rtotal
• I-total
• Voltages

66
Analyze series-parallel

• Requiv
• Rtotal
• I-total
• Voltages

67
Analyze series-parallel

• Requiv
• Rtotal
• I-total
• Voltages