Welcome to Lesson 1! ๐
ใฌใในใณ1ใธใใใใ๏ผ
In this lesson, you will learn the fundamental principles of electricity that power all automotive systems. Understanding these basics is essential for diagnosing and repairing electrical problems.
ใใฎใฌใในใณใงใฏใใในใฆใฎ่ชๅ่ปใทในใใ ใซ้ปๅใไพ็ตฆใใ้ปๆฐใฎๅบๆฌๅ็ใๅญฆใณใพใใใใใใฎๅบ็คใ็่งฃใใใใจใฏใ้ปๆฐ็ๅ้กใ่จบๆญใไฟฎ็ใใใใใซไธๅฏๆฌ ใงใใ
โ What is electricity and how it flows
โ Voltage, Current, and Resistance
โ Ohm’s Law and practical calculations
โ Series and Parallel circuits
โ Electrical safety procedures
This lesson takes approximately 4-5 hours to complete, including the quiz at the end.
What is Electricity? โก
้ปๆฐใจใฏ๏ผ
Electricity is the flow of electrons through a conductor. In automotive systems, electricity powers everything from the engine control unit (ECU) to the headlights.
้ปๆฐใจใฏใๅฐไฝใ้ใ้ปๅญใฎๆตใใงใใ่ชๅ่ปใทในใใ ใงใฏใใจใณใธใณๅถๅพกใฆใใใ๏ผECU๏ผใใใใใใฉใคใใพใงใใในใฆใซ้ปๆฐใไฝฟใใใฆใใพใใ
้ปๅญใฏ่ฒ ๆฅต(-)ใใๆญฃๆฅต(+)ใธๆตใใ
In a 12V automotive battery, electrons flow at nearly the speed of light (about 300,000 km/s), but the actual drift velocity of individual electrons is only about 1 mm/s!
Key Electrical Concepts ๐
้่ฆใช้ปๆฐ็ๆฆๅฟต
Voltage (V) ๐
้ปๅง๏ผใใซใ๏ผ
Voltage is the electrical pressure that pushes electrons through a circuit. It is measured in Volts (V).
้ปๅงใฏใๅ่ทฏใ้ใฃใฆ้ปๅญใๆผใ้ปๆฐ็ๅงๅใงใใใใซใ๏ผV๏ผใงๆธฌๅฎใใใพใใ
๐งโก๏ธ Low Pressure = Low Voltage
ใใคใๅ ใฎๆฐดๅงใฎใใใซใ้ปๅงใ้ซใใปใฉๆผใๅใๅผทใ
Most passenger vehicles use a 12V electrical system.
Large trucks and buses use 24V systems.
Hybrid/Electric vehicles use 200-800V systems.
Current (I) โก
้ปๆต๏ผใขใณใใข๏ผ
Current is the flow rate of electrons through a circuit. It is measured in Amperes (A).
้ปๆตใฏใๅ่ทฏใๆตใใ้ปๅญใฎๆต้ใงใใใขใณใใข๏ผA๏ผใงๆธฌๅฎใใใพใใ
๐งโก๏ธ Low Flow = Low Current
ใใคใใๆตใใๆฐดใฎๆต้ใฎใใใซใ้ปๆตใๅคงใใใปใฉๅคใใฎ้ปๅญใๆตใใ
High current can cause wires to overheat and start fires. Always use the correct wire gauge and fuse rating!
Resistance (R) ๐ง
ๆตๆ๏ผใชใผใ ๏ผ
Resistance is the opposition to the flow of current. It is measured in Ohms (ฮฉ).
ๆตๆใฏใ้ปๆตใฎๆตใใซๅฏพใใๆตๆใงใใใชใผใ ๏ผฮฉ๏ผใงๆธฌๅฎใใใพใใ
โญ Wide Pipe = Low Resistance
ใใคใๅ ใฎ้ๅฎณ็ฉใฎใใใซใๆตๆใๅคงใใใปใฉ้ปๆตใๅฐใชใใชใ
Ohm’s Law ๐
ใชใผใ ใฎๆณๅ
Ohm’s Law is the most fundamental formula in electrical theory. It describes the relationship between voltage, current, and resistance.
ใชใผใ ใฎๆณๅใฏใ้ปๆฐ็่ซใซใใใๆใๅบๆฌ็ใชๅ ฌๅผใงใใ้ปๅงใ้ปๆตใๆตๆใฎ้ขไฟใ่กจใใพใใ
I = Current (Amperes) | ้ปๆต๏ผใขใณใใข๏ผ
R = Resistance (Ohms) | ๆตๆ๏ผใชใผใ ๏ผ
If you know any TWO values, you can calculate the THIRD using Ohm’s Law!
Three Forms of Ohm’s Law ๐ข
ใชใผใ ใฎๆณๅใฎ3ใคใฎๅฝข
ๆฑใใใใใฎใ้ ใใจใๅ ฌๅผใ็พใใพใ๏ผ
Practice Problem 1 ๐งฎ
็ทด็ฟๅ้ก1
A headlight bulb has a resistance of 2ฮฉ and is connected to a 12V battery.
Question: What is the current flowing through the bulb?
ใใใใฉใคใใใซใใฎๆตๆใ2ฮฉใงใ12Vใใใใชใผใซๆฅ็ถใใใฆใใพใใ
ๅ้ก: ใใซใใๆตใใ้ปๆตใฏไฝใขใณใใขใงใใ๏ผ
Step 1: Identify what you know
โข V = 12V | โข R = 2ฮฉ | โข I = ?
Step 2: Choose the correct formula
โข I = V รท R
Step 3: Calculate
โข I = 12V รท 2ฮฉ = 6A
The current flowing through the headlight bulb is 6 Amperes (6A).
ใใใใฉใคใใใซใใๆตใใ้ปๆตใฏ6ใขใณใใข๏ผ6A๏ผใงใใ
Practice Problem 2 ๐งฎ
็ทด็ฟๅ้ก2
A starter motor draws 150A from a 12V battery.
Question: What is the resistance of the starter motor?
ในใฟใผใฟใผใขใผใฟใผใ12Vใใใใชใผใใ150Aใๅผใๅบใใพใใ
ๅ้ก: ในใฟใผใฟใผใขใผใฟใผใฎๆตๆใฏไฝใชใผใ ใงใใ๏ผ
Step 1: Identify what you know
โข V = 12V | โข I = 150A | โข R = ?
Step 2: Choose the correct formula
โข R = V รท I
Step 3: Calculate
โข R = 12V รท 150A = 0.08ฮฉ
The resistance of the starter motor is 0.08 Ohms (0.08ฮฉ).
ในใฟใผใฟใผใขใผใฟใผใฎๆตๆใฏ0.08ใชใผใ ๏ผ0.08ฮฉ๏ผใงใใ
Series Circuit ๐
็ดๅๅ่ทฏ
In a series circuit, components are connected in a single path, one after another. Current flows through each component in sequence.
็ดๅๅ่ทฏใงใฏใ้จๅใๅไธ็ต่ทฏใงๆฌกใ ใซๆฅ็ถใใใพใใ้ปๆตใฏๅ้จๅใ้ ็ชใซๆตใใพใใ
ๅไธ็ต่ทฏใงๆฅ็ถใใใ้จๅ
โ Current is the SAME through all components
โ Voltage is DIVIDED among components
โ Total resistance = R1 + R2 + R3…
โ If ONE component fails, the ENTIRE circuit stops
Series circuits are rarely used in automotive systems because if one component fails, everything stops working!
Parallel Circuit โก
ไธฆๅๅ่ทฏ
In a parallel circuit, components are connected across multiple paths. Each component has its own direct connection to the power source.
ไธฆๅๅ่ทฏใงใฏใ้จๅใ่คๆฐใฎ็ต่ทฏใงๆฅ็ถใใใพใใๅ้จๅใฏ้ปๆบใธใฎ็ดๆฅๆฅ็ถใๆใฃใฆใใพใใ
โโ๐ก
โโ๐ก ๐
่คๆฐ็ต่ทฏใงๆฅ็ถใใใ้จๅ
โ Voltage is the SAME across all components
โ Current is DIVIDED among branches
โ Total resistance is LESS than the smallest resistor
โ If ONE component fails, OTHERS continue to work
Most automotive electrical components (lights, accessories) are connected in PARALLEL so that if one fails, others continue to operate!
Series vs Parallel ๐
็ดๅ vs ไธฆๅ
โข Voltage divides
โข One fails = all fail
โข R_total = R1 + R2 + R3
โข Current divides
โข One fails = others work
โข R_total < smallest R
Series: Old Christmas lights (one bulb out = all out)
Parallel: Car headlights (one burns out, other still works)
โ SERIES = Not practical
Circuit Practice Problem ๐งฎ
ๅ่ทฏ็ทด็ฟๅ้ก
Three 12V light bulbs are connected in PARALLEL to a 12V battery. Each bulb has a resistance of 6ฮฉ.
Question: What is the total current drawn from the battery?
3ใคใฎ12V้ป็ใ12Vใใใใชใผใซไธฆๅๆฅ็ถใใใฆใใพใใๅ้ป็ใฎๆตๆใฏ6ฮฉใงใใ
ๅ้ก: ใใใใชใผใใๅผใๅบใใใ็ท้ปๆตใฏ๏ผ
Step 1: Each bulb gets full 12V (parallel)
Step 2: Current per bulb: I = V รท R = 12V รท 6ฮฉ = 2A
Step 3: Total current = 2A + 2A + 2A = 6A
Total current drawn from the battery is 6 Amperes (6A).
ใใใใชใผใใๅผใๅบใใใ็ท้ปๆตใฏ6ใขใณใใข๏ผ6A๏ผใงใใ
Electrical Safety โ ๏ธ
้ปๆฐๅฎๅ จ
Working with automotive electrical systems requires strict adherence to safety procedures. Even 12V systems can be dangerous if not handled properly.
่ชๅ่ป้ปๆฐใทในใใ ใฎไฝๆฅญใซใฏใๅฎๅ จๆ้ ใฎๅณๆ ผใช้ตๅฎใๅฟ ่ฆใงใใ12Vใทในใใ ใงใใ้ฉๅใซๆฑใใชใใจๅฑ้บใงใใ
Hybrid and Electric Vehicles:
โข Use 200-800V systems
โข Can be LETHAL
โข Only CERTIFIED technicians should work on HV systems!
ใใคใใชใใ่ปใ้ปๆฐ่ชๅ่ปใฏ200๏ฝ800Vใฎใทในใใ ใไฝฟ็จใใฆใใใ่ดๅฝ็ใซใชใๅฏ่ฝๆงใใใใพใ๏ผ
Even 12V systems can cause:
โข Burns from short circuits
โข Fires from overheated wires
โข Explosions from battery gases
โข Eye injuries from sparks
Safety Procedures ๐ฆบ
ๅฎๅ จๆ้
- Disconnect the Battery | ใใใใชใผใๅๆญ
Always disconnect the NEGATIVE (-) terminal FIRST before working on electrical systems. - Use Proper Tools | ้ฉๅใชๅทฅๅ
ทใไฝฟ็จ
Use insulated tools rated for electrical work. - Wear PPE | PPEใ็็จ
Safety glasses, insulated gloves, and non-conductive footwear. - Check for Shorts | ใทใงใผใใ็ขบ่ช
Use a multimeter to check for short circuits before connecting power. - Avoid Water | ๆฐดใ้ฟใใ
Never work on electrical systems in wet conditions. - Follow Service Manual | ใตใผใในใใใฅใขใซใซๅพใ
Always refer to the manufacturer’s procedures.
When disconnecting battery: 1. Negative (-) FIRST, 2. Positive (+) SECOND
When reconnecting battery: 1. Positive (+) FIRST, 2. Negative (-) SECOND
Common Electrical Hazards โ ๏ธ
ไธ่ฌ็ใช้ปๆฐ็ๅฑ้บ
Fire Safety ๐ฅ
็ซ็ฝๅฎๅ จ
Short circuits can cause wires to overheat and start fires!
็ญ็ตกใซใใ้
็ทใ้็ฑใใ็ซ็ฝใ็บ็ใใๅฏ่ฝๆงใใใใพใ๏ผ
Fire Prevention | ็ซ็ฝไบ้ฒ
- Always use the correct fuse rating
- Never bypass fuses with wire or higher-rated fuses
- Use proper wire gauge for the current load
- Inspect wires for damage or wear
- Keep flammable materials away from electrical work
- Have a fire extinguisher nearby (Class C for electrical fires)
1. Disconnect battery immediately
2. Use Class C fire extinguisher
3. Never use water on electrical fires!
4. Evacuate if fire spreads
5. Call emergency services
Personal Protective Equipment (PPE) ๐ฆบ
ๅไบบ็จไฟ่ญทๅ ท
โข Metal jewelry (rings, watches, bracelets)
โข Wet or damp clothing
โข Loose clothing that can catch on equipment
โข Metal-framed glasses (use plastic frames)
Battery Safety ๐
ใใใใชใผๅฎๅ จ
Car batteries produce hydrogen gas which is highly explosive!
A single spark can cause a battery to explode!
่ชๅ่ป็จใใใใชใผใฏๆฐด็ด ใฌในใ็บ็ใใใ้ๅธธใซ็็บๆงใ้ซใใงใ๏ผ
Battery Safety Rules | ใใใใชใผๅฎๅ จ่ฆๅ
- No sparks or flames near battery
- Work in well-ventilated area
- Wear safety glasses and gloves
- Remove metal jewelry
- Never lean over battery while working
- Check for cracks or leaks
1. Connect positive (+) to dead battery
2. Connect positive (+) to good battery
3. Connect negative (-) to good battery
4. Connect negative (-) to ENGINE BLOCK (not dead battery!)
5. Start good car, then dead car
6. Disconnect in REVERSE order
๐ Lesson 1 Quiz
ใฌใในใณ1ใฏใคใบ
Congratulations on completing all the learning content! Now it’s time to test your knowledge with a 10-question quiz.
ใในใฆใฎๅญฆ็ฟใณใณใใณใใๅฎไบใใพใใ๏ผ10ๅใฎใฏใคใบใง็ฅ่ญใใในใใใพใใใใ
โข 10 multiple-choice questions
โข Passing score: 70% (7/10 correct)
โข You can review your answers after completion
โข Take your time and read carefully
โข 10ๅใฎ้ธๆๅ้ก
โข ๅๆ ผ็น๏ผ70%๏ผ10ๅไธญ7ๅๆญฃ่งฃ๏ผ
โข ๅฎไบๅพใซ็ญใใ็ขบ่ชใงใใพใ
โข ๆ้ใใใใฆๆ
้ใซ่ชญใใงใใ ใใ
โ What electricity is and how it flows
โ Voltage, Current, and Resistance
โ Ohm’s Law and calculations
โ Series and Parallel circuits
โ Electrical safety procedures
Click “Next” to begin the quiz. Good luck!
ใๆฌกใธใใใฏใชใใฏใใฆใฏใคใบใ้ๅงใใพใใ้ ๅผตใฃใฆใใ ใใ๏ผ
ๅ้ก1: ใปใจใใฉใฎไน็จ่ปใฎ้ปๆฐใทในใใ ใฎๆจๆบ้ปๅงใฏไฝใใซใใงใใ๏ผ
ๆญฃ่งฃใฏB) 12Vใงใใใปใจใใฉใฎไน็จ่ปใฏ12V้ปๆฐใทในใใ ใไฝฟ็จใใฆใใพใใ
ๅ้ก2: ใชใผใ ใฎๆณๅใซใใใฐใ้ปๅงใๅขๅ ใๆตๆใๅใใพใพใฎๅ ดๅใ้ปๆตใฏใฉใใชใใพใใ๏ผ
ๆญฃ่งฃใฏB) ้ปๆตใฏๅขๅ ใใใงใใใชใผใ ใฎๆณๅ๏ผI = V รท R๏ผใซใใใ้ปๅงใๅขๅ ใๆตๆใไธๅฎใชใใ้ปๆตใฏๆฏไพใใฆๅขๅ ใใพใใ
ๅ้ก3: ๅ่ทฏใ12Vใง3Aใๅผใๅบใใพใใๆตๆใฏไฝใชใผใ ใงใใ๏ผ
ๆญฃ่งฃใฏB) 4ฮฉใงใใใชใผใ ใฎๆณๅใไฝฟ็จ๏ผR = V รท I = 12V รท 3A = 4ฮฉใ
ๅ้ก4: ็ดๅๅ่ทฏใง1ใคใฎ้จๅใๆ ้ใใใจใใฉใใชใใพใใ๏ผ
ๆญฃ่งฃใฏB) ๅ่ทฏๅ จไฝใๅๆญขใใใงใใ็ดๅๅ่ทฏใงใฏใใในใฆใฎ้จๅใๅใ้ปๆต็ต่ทฏใๅ ฑๆใใฆใใพใใ
ๅ้ก5: ่ชๅ่ปใฎใฉใคใใซๆใใใไฝฟ็จใใใๅ่ทฏใฎใฟใคใใฏ๏ผ
ๆญฃ่งฃใฏB) ไธฆๅๅ่ทฏใงใใ่ชๅ่ปใฎใฉใคใใฏไธฆๅใซๆฅ็ถใใใฆใใใใใ1ใคใฎ้ป็ใๆ ้ใใฆใไปใฏๅไฝใ็ถใใพใใ
ๅ้ก6: ่ชๅ่ป้ปๆฐใทในใใ ใฎไฝๆฅญๆใซๆๅใซๅๆญใในใใใฎใฏ๏ผ
ๆญฃ่งฃใฏB) ่ฒ ๆฅต๏ผ-๏ผ็ซฏๅญใงใใ็ญ็ตกใ็ซ่ฑใ้ฒใใใใๅธธใซ่ฒ ๆฅต็ซฏๅญใๆๅใซๅๆญใใพใใ
ๅ้ก7: ้ปๆฐๆตๆใฎๆธฌๅฎๅไฝใฏ๏ผ
ๆญฃ่งฃใฏC) ใชใผใ ๏ผฮฉ๏ผใงใใๆตๆใฏๅธธใซใชใผใ ใงๆธฌๅฎใใใพใใ
ๅ้ก8: ็ญ็ตก๏ผใทใงใผใ๏ผใจใฏไฝใงใใ๏ผ
ๆญฃ่งฃใฏB) ๆๅณใใชใไฝๆตๆ็ต่ทฏใงใใ็ญ็ตกใฏ้ปๆตใ้ๅธธใซไฝใๆตๆใฎๆๅณใใชใ็ต่ทฏใ้ใใจใใซ็บ็ใใพใใ
ๅ้ก9: ไธฆๅๅ่ทฏใงใฏใใในใฆใฎๅๅฒใงไฝใๅใใงใใ๏ผ
ๆญฃ่งฃใฏB) ้ปๅงใงใใไธฆๅๅ่ทฏใงใฏใ้ปๅงใฏใในใฆใฎๅๅฒใงๅใใงใใใ้ปๆตใฏๅๅฒ้ใงๅๅฒใใใพใใ
ๅ้ก10: ้ปๆฐ็ซ็ฝใซใฏใฉใฎใฟใคใใฎๆถ็ซๅจใไฝฟ็จใในใใงใใ๏ผ
ๆญฃ่งฃใฏC) ใฏใฉในC๏ผ้ปๆฐ็จ๏ผใงใใใฏใฉในCๆถ็ซๅจใฏ้ปๆฐ็ซ็ฝๅฐ็จใซ่จญ่จใใใฆใใพใใ้ปๆฐ็ซ็ฝใซๆฐดใไฝฟ็จใใชใใงใใ ใใ๏ผ
็ตๆใ่จ็ฎไธญ…
You’re now ready to move on to Lesson 2: Charging System where you’ll learn about batteries, alternators, and voltage regulators!
