Activity 1.1.1 — General Safety in the Electronics Classroom¶

Learning Objectives¶

By the end of this lesson, students will be able to:

List and follow general safety rules for the electronics classroom
Identify appropriate fire extinguishers for electrical fires
Describe the hazards of electrical injuries
Demonstrate proper measurement techniques to avoid circuit faults
Explain why safety rules exist and how to enforce them with peers

Vocabulary¶

Vocabulary (click to expand)

Term	Definition
Electrocution	Death or serious injury caused by electric shock
Insulator	A material that does not conduct electricity (e.g., rubber, glass)
Conductor	A material that allows electricity to flow through it (e.g., copper, gold)
Ground	A reference point of zero voltage; safety connection to Earth
Short circuit	An unintended path with little or no resistance
Ohm	The unit of electrical resistance (symbol: Omega)

Part 1: General Safety Rules¶

The electronics classroom contains equipment, tools, and materials that can cause injury if not handled properly. Your safety — and the safety of your classmates — depends on following these rules consistently.

Core Safety Principles¶

Follow procedures exactly
Always read procedures before starting any lab activity
Never take shortcuts or skip steps
Ask the instructor if you are unsure about any procedure
Read manuals and documentation
Equipment manuals contain important safety information
If you do not know how to use something, ask first
Never disable safety devices
Do not remove or bypass fuses, guards, or safety interlocks
These devices exist to protect you
Avoid wet areas and liquids
Water conducts electricity and can create dangerous pathways
Keep drinks and liquids away from work areas
Dry your hands before touching equipment
Remove jewelry and loose items
Metal jewelry (rings, watches, bracelets) can accidentally conduct electricity
Tie back long hair to prevent it from catching in equipment
Assume circuits are always ON
Never assume a circuit is off — verify with a meter
Some components store dangerous charges even when disconnected
Be especially careful around capacitors
Use proper measurement techniques
Use a voltmeter to verify circuits are de-energized
Select the correct measurement mode (voltage, current, resistance)
Connect meters properly to avoid short circuits

Part 2: Fire Safety¶

Electrical equipment can overheat and cause fires if used improperly.

Types of Fire Extinguishers¶

Class	Type of Fire	Symbol	Examples
A	Ordinary combustibles	Green triangle with "A"	Wood, paper, trash
B	Flammable liquids	Red square with "B"	Gasoline, oil, paint
C	Electrical equipment	Blue circle with "C"	Wiring, motors, outlets
D	Combustible metals	Yellow star with "D"	Magnesium, titanium

For electrical fires (Class C): - Use a CO2 or dry chemical extinguisher - Never use water on electrical fires — water conducts electricity! - Disconnect power if possible before attempting to extinguish

Fire Prevention Tips¶

Keep work areas clean and free of clutter
Do not overload circuits or power strips
Inspect cords and cables for damage before use
Report any burning smell or sparking immediately

Part 3: Chemical Safety¶

Some electronic components and materials contain hazardous chemicals.

Common Hazards¶

Material	Hazard	Precaution
Solder	Contains lead (toxic)	Wash hands after handling; do not eat/drink at workstation
Flux	Irritant, fumes	Work in ventilated area; avoid breathing fumes
Battery acid	Corrosive	Handle leaking batteries with care; neutralize with baking soda
Cleaning solvents	Flammable, toxic	Use in fume hood; store properly

Safe Handling Practices¶

Always wash your hands after handling electronic components
Never eat or drink while working at your bench
Store chemicals in designated areas with proper labels
Dispose of materials in designated hazardous waste containers

Part 4: Electrical Injuries¶

Electricity can cause serious injury or death. Understanding the hazards helps you avoid them.

How Electricity Affects the Body¶

The severity of an electrical injury depends on: - Current (amps) — Higher current is more dangerous - Path through the body — Current through the heart is most dangerous - Duration — Longer exposure causes more damage - Frequency — AC at 60 Hz is particularly dangerous to the heart

Danger Levels of Current¶

Current	Effect
1 mA	Threshold of perception (tingling)
10 mA	Painful shock, muscle contraction
30-75 mA	Respiratory paralysis, possible death
75-250 mA	Ventricular fibrillation (heart stops pumping) — often fatal
250+ mA	Severe burns, heart may stop but may restart

Why the Danger Varies¶

The same voltage can cause different current levels depending on skin resistance:

Ohm's Law: I = V / R

- Dry skin: ~100,000 ohms (relatively safe)
- Wet skin: ~1,000 ohms (much more dangerous)
- Broken skin (internal): ~100 ohms (very dangerous)

This is why you should never work on circuits with wet hands!

Types of Electrical Injuries¶

Electrocution (death) — Current disrupts the heart's electrical rhythm
Burns — Tissue damage from heat generated by current flow
Chemical exposure — Internal burns if current causes tissue breakdown
Wounds — Current entering and exiting the body creates burns at contact points

Key insight: Voltage alone does not determine danger — it is the current flowing through your body that causes injury. Even "low voltage" systems can be lethal if resistance is low (e.g., wet skin).

Part 5: Protecting Yourself¶

Safe Work Habits¶

Always disconnect power before working on circuits
Use the proper tools for each task
Keep your workspace organized and clean
Work deliberately — rushing leads to mistakes
If something does not look right, stop and investigate

Double-Check Before You Touch¶

Before touching any circuit: 1. Is power disconnected? 2. Have you measured with a multimeter to confirm zero volts? 3. Are capacitors discharged (if present)? 4. Is your body properly grounded (no static electricity)?

Summary¶

General Safety: Follow procedures, read manuals, never disable safety devices, avoid wet areas, remove jewelry, assume circuits are ON
Fire Safety: Use Class C extinguishers for electrical fires; never use water on electrical fires
Chemical Safety: Wash hands, avoid eating/drinking at workstation, handle hazardous materials properly
Electrical Injuries: Current (not voltage) causes injury; even low voltages can be dangerous with low body resistance
Prevention: Verify circuits are de-energized, work deliberately, ask if unsure

Key Reminders¶

Always assume a circuit is live until you personally verify it is off
Never disable safety devices or bypass fuses
Remove all metal jewelry before working with circuits
Use the correct fire extinguisher (Class C) for electrical fires
Dry hands dramatically reduce body resistance — never work with wet hands
Keep food and drinks away from electronics work areas
If you see a classmate violating safety rules, remind them — you are responsible for each other's safety

Custom activity — adapted from PLTW Digital Electronics