1. Laboratory Safety: Electricity
Richard Ho
Arthur Lee

2. Introduction and Importance
Understand scientific fundamentals of electricity
Identify causes of electrical hazards
Safety and precautions with electrical devices

3. Fundamental Concepts Work (W) Power (P) Electric Charge (Q)
SI units is the Joule: J
Energy is the ability to do Work, and has the same units as Work
Power (P)
Power is the rate at which work is done: P = dW/dt
Measures how fast energy is released
Electric Charge (Q)
SI unit of charge is the coulomb: C
A proton has a charge of × C
An electron has a charge of × C
Electric Current (I)
SI unit of electric current is the ampere: A = C/s
The rate at which charge flows through a substance: I = dQ/dt

4. Fundamental Concepts
Electric Potential (V) = Electric pressure = Voltage
SI unit of electric potential is the volt: V = J/C
Potential energy per unit charge across an electric field
Resistance (R)
SI unit of resistance is the ohm: Ω = V/A
Measure of opposition to current: I = V/R
Conductors have very low resistance
Ions in solution can conduct electricity
Insulators have very high resistances

5. Formulas to Remember

6. Static Electricity
A accumulation of charge in an object creates a difference in charge between the object and its surrounding
Electric shock may occur if the buildup of charge in one object is transferred to another object in a short interval of time
Friction can displace electrons and create differences in charge
Buildup of charge in clouds dissipate via lightning

7. Current
Body fluids contain dissolved ions that can conduct electricity
It’s not voltage that kills... it’s current:
Approximate figures1 (depends on body chemistry)
DC (men)
DC (women)
60 Hz AC (men)
60 Hz AC (women)
Slight tingling at hands
1.0 mA
0.6 mA
0.4 mA
0.3 mA
Threshold of perception
5.2 mA
3.5 mA
1.1 mA
0.7 mA
Painful, but still can control muscles
62 mA
41 mA
9 mA
6 mA
Very painful, lose control of muscles
76 mA
51 mA
16 mA
10.5 mA
Severe pain, difficulty breathing
90 mA
60 mA
23 mA
15 mA
Fibrillation of heart (FATAL)
500 mA
100 mA
1) Online Reference:

8. Human Body’s Resistance
Clean dry skin can have as much as 40 kΩ to 1 MΩ resistance, but WATER CAN GREATLY REDUCE RESISTANCE
Approximate Figures1
DRY
WET
Wire touched by finger
40 kΩ to 1 MΩ
4 kΩ to 15 kΩ
Wire held by hand
15 kΩ to 50 kΩ
3 kΩ to 5 kΩ
Metal pliers held by hand
5 kΩ to 10 kΩ
1 kΩ to 3 kΩ
Contact with palm of hand
3 kΩ to 8 kΩ
1 kΩ to 2 kΩ
1.5 inch metal pipe grasped by one hand
500 Ω to 1500 Ω
1.5 inch metal pipe grasped by two hands
250 Ω to 750 Ω
Hand immersed in conductive liquid
200 Ω to 500 Ω
Foot immersed in conductive liquid
100 Ω to 300 Ω
1) Online Reference:

9. How much voltage can kill
Ohm’s law: V = I R
Resistance of dry skin can reach into the MΩ range
Resistance of wet skin is around 300 Ω to 1000 Ω
Suppose 80 mA can kill. If you touch an exposed wire (1 MΩ), it takes about 80 mA × 1000 kΩ = 80 kV to kill. If you touch the wire with wet skin (300 Ω), it only takes about 24 V.
In the United States, standard electrical outlets have 60 Hz AC power at 120 V. Touching an exposed wire with a dry hand at 15 kΩ will give you 8 mA, a painful shock. With a wet hand, the same 120 V will deliver a 400 mA shock, which causes death.
High resistance can cause electric burns, even if it causes no electric shock

10. Safety Guidelines
Use three-pronged power cords and receptacles to ensure proper grounding
Avoid extension cords if possible
Use properly insulated wires and connections
Do not handle connections with wet hands or while standing on wet floor
Avoid operating instruments that are placed on metal surfaces, such as metal carts
Do not operate wet electrical equipment (unless it is intended to be used in this way) or devices with chemicals spilled on them
Be certain that electronic equipment has adequate ventilation to avoid overheating

11. Safety Guidelines
Never attempt to trouble-shoot or repair the electronics of an instrument unless you are trained to do so
Never touch the outside of a leaking electrophoresis gel box, or one with a puddle under it, if it is plugged into a power supply
In case of an electrical fire:
If an instrument is smoking or has burning odor, turn it off and unplug it immediately
Use only a carbon dioxide-type fire extinguisher
Some electrical components (selenium rectifiers) emit poisonous fumes when burning

12. Instrument Malfunction
Is the instrument plugged in?
Is the power on?
If there is a power strip, is it turned on?
Is the wall outlet functioning?
Is the power cord frayed
Is there a blown fuse or tripped circuit breaker?
Is there an accessible bulb that needs replacement?
Try pressing the “reset” button if there is one.
Is there a 110 or 220V switch? Is it properly set?
Try unplugging the instrument and plug it back in.
Go annoy the manufacturer

13. Remember this
REMEMBER TO NEVER EVER HANDLE ELECTRICAL CONNECTIONS WITH WET HANDS!!!!!!!!!!!!

14. Signs that indicate potential hazards

15. Also stay away from this guy
2.718 MV
1.414 MV

16. Thank you for paying attention.
Any questions?