Automotive Electrical & Electronic Systems Classroom Manual

Page 87

ker88839_ch05.qxd

1/9/06

11:24 AM

Page 75

Series, Parallel, and Series-Parallel Circuits

75

before calculating total current. When performing calculation on a parallel circuit, it should be remembered that more current will always flow through the path with the least resistance. Kirchhoff’s Law of Current (Kirchhoff’s 1st Law) states that the current flowing into a junction or point in an electrical circuit must equal the current flowing out.

PARALLEL CIRCUIT VOLTAGE DROPS In a parallel circuit, each branch drops the same voltage, regardless of the resistance. If the resistance values are not the same, then different amounts of current will flow in each branch (Figure 5-6). According to Kirchhoff’s Law of Current, the current that flows through a parallel circuit divides into each path in the circuit: When the current flow in each path is added, the total current will equal the current flow leaving the power source. When calculating the current flow in parallel circuits, each current flow path must be treated as a series circuit or the total resistance of the circuit must be calculated

Parallel Circuit Voltage Drops Exercise Exercise Objective: Demonstrate that all branches of a parallel circuit drop an equal amount of voltage. In a parallel circuit, each branch drops the same voltage, regardless of the resistance. If the resistance values are not the same, then a different amount of current flows in each branch. Assemble the circuit shown in Figure 5-7. Measure voltage between each of the following pairs of points and record the readings. Record Measurements: 1 to 2 ______________________________volts 3 to 4 ______________________________volts 5 to 6 ______________________________volts 7 to 8 ______________________________volts Are the voltage drops in the three branches equal?________ Does the sum of the 3-4, 5-6, and 7-8 voltage drops equal the supply voltage?________ Should it?________ Why do you think all branches of a parallel circuit drop an equal amount of voltage?

Figure 5-5. Series circuit voltage drop exercise. (GM Service and Parts Operations)

20V

Figure 5-6.

BRANCH #1 4A

BRANCH #2 2A

BRANCH #3 2.9A

5Ω

10Ω

7Ω

20V

20V

20V

Parallel circuit voltage drops.

Et = 20V Rt = 0.4Ω It = 8A IB1 = 4A IB2 = 2A IB3 = 2.9A EB1 = 20V EB2 = 20V EB3 = 20V


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Summary

4min
page 363

Cruise Control Systems

3min
pages 357-358

Review Questions

3min
pages 364-366

Radios and Entertainment Systems

6min
pages 337-339

Theft Deterrent Systems

7min
pages 353-356

Heated Seats

6min
pages 343-345

Power Seats

2min
pages 341-342

Power Door Locks, Trunk Latches, and Seat- Back Releases

2min
page 346

Heating and Air-Conditioning Systems

12min
pages 328-334

Class 2 IPM-Controlled HVAC Systems

2min
pages 335-336

Review Questions

1min
page 326

Summary

1min
page 325

Windshield Wipers and Washers

10min
pages 319-324

Summary

1min
page 314

Review Questions

2min
pages 315-316

Head-Up Display (HUD

5min
pages 311-313

Electromagnetic Instrument Circuits

11min
pages 296-300

Review Questions

2min
pages 293-294

Malfunction Indicator Lamp (MIL

5min
pages 301-303

Summary

1min
page 292

Instrument Panel and Interior Lamp Circuits

4min
pages 289-291

Circuits

1min
page 288

Backup Lamp Circuits Side Marker and Clearance Lamp

1min
page 287

Circuits

2min
page 286

Stop Lamp and Turn Signal Circuits Hazard Warning Lamp (Emergency Flasher)

6min
pages 282-285

Taillamp, License Plate Lamp, and Parking Lamp Circuits

1min
page 281

Common Automotive Bulbs

1min
page 280

Headlamp Circuits

16min
pages 270-279

Summary

1min
page 267

Review Questions

1min
page 268

Spark Plug Construction

4min
pages 264-266

Distributor Cap and Rotor

3min
pages 259-261

Primary and Secondary Circuits

1min
page 248

Voltages

4min
pages 246-247

Basic Circuits and Current

1min
page 241

Silicon-Controlled Rectifiers (SCRs

1min
page 233

Review Questions

2min
pages 236-238

Summary

1min
page 235

Transistors

9min
pages 229-232

Rectifier Circuits

2min
page 228

Semiconductors

7min
pages 222-224

Photonic Semiconductors

2min
page 227

Review Questions

3min
pages 218-220

Starter Motor and Drive Types

8min
pages 210-214

DC Starter Motor Operation

5min
pages 206-208

Summary

2min
pages 216-217

Overrunning Clutch

1min
page 215

Specific Starting Systems

6min
pages 200-203

Summary

2min
pages 191-192

Differences

13min
pages 183-190

Review Questions

3min
pages 193-194

Charge/Voltage/Current Indicators

3min
pages 180-181

Solid-state Regulators

9min
pages 175-179

Electromagnetic Regulators

1min
page 174

Voltage Regulation

2min
page 173

Current Production in an AC Generator

9min
pages 168-172

Diode Rectification

3min
pages 162-163

AC Generator (Alternator) Components

7min
pages 164-167

Review Questions

4min
pages 157-158

Battery Installations

4min
pages 150-151

Battery Installation Components

2min
pages 152-153

Summary

2min
page 156

Battery Life and Performance Factors

5min
pages 154-155

State-of-Charge Indicators Wet-Charged and Dry-Charged

2min
page 147

Battery Electrolyte

2min
page 146

Electrochemical Action

8min
pages 142-145

Review Questions

3min
pages 138-140

Wire Color Coding

2min
pages 121-122

Multiplex Circuits

8min
pages 112-114

Ground Paths

2min
page 111

Connectors and Terminals

5min
pages 108-110

Wire Size

6min
pages 105-107

Wire Types and Materials

2min
page 104

Wiring and Harnesses

2min
pages 102-103

Review Questions

4min
pages 97-100

Parallel Circuit Voltage Drops Calculating Series Circuit Total

1min
page 87

Series and Parallel Circuit Faults

3min
pages 94-95

Series-Parallel Circuits

4min
pages 91-93

Review Questions

2min
page 82

Summary

3min
pages 80-81

Electromagnetism

9min
pages 67-71

Electromagnetic Induction

11min
pages 72-76

Magnetism

2min
page 66

Power

2min
page 56

Capacitance

8min
pages 57-60

Review Questions

2min
pages 62-64

Summary

1min
page 61

Complete Electrical Circuit

3min
pages 52-53

Summary

2min
page 43

Historical Figures in Electricity

2min
page 42

Fire Extinguishers

1min
page 31

Safety Tips for Technicians

2min
pages 25-26

Nuts

1min
page 15

Review Questions

2min
pages 44-46

Electrical Cord Safety

1min
pages 29-30

Safety in Lifting (Hoisting) a Vehicle

2min
pages 27-28
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