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Laboratory Safety: Electricity

Laboratory Safety: Electricity. Richard Ho Arthur Lee. Introduction and Importance. Understand scientific fundamentals of electricity Identify causes of electrical hazards Safety and precautions with electrical devices. Fundamental Concepts. Work (W) SI units is the Joule: J

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Laboratory Safety: Electricity

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  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) • 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 1.602 × 10-19 C • An electron has a charge of -1.602 × 10-19 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: 1) Online Reference: http://www.allaboutcircuits.com/vol_1/chpt_3/4.html

  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 1) Online Reference: http://www.allaboutcircuits.com/vol_1/chpt_3/4.html

  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?

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