Dangers of Electricity
Simple Explanation
Electric shock happens when current flows through the body, I=V/R β and because wet skin has far lower resistance than dry skin, the SAME voltage can produce a far more dangerous shock current under wet conditions.
Why Do We Need It?
Understanding this relationship explains genuinely life-saving safety practices β why electrical devices must never be used with wet hands, and why earthing and circuit breakers exist at all.
Formula
Electric Shock Current
I = V/R
The current that flows through a person's body during an electric shock depends on the voltage they contact and their body's own resistance β a simple application of Ohm's law, but with genuinely dangerous consequences.
- I
- β current flowing through the body, in amperes (A)
- V
- β voltage the body is exposed to, in volts (V)
- R
- β the body's electrical resistance, in ohms (Ξ©) β far lower when skin is wet than when dry
When to use it: Whenever estimating the danger of an electric shock from a given voltage and the body's resistance under those conditions.
Worked Example
Estimate the danger of a shock under wet conditions
A person with wet skin (resistance 1000 ohms) touches a 230 V household circuit. Find the current that flows through their body.
Why Does This Work?
This is a direct application of Ohm's law to the human body treated as a resistor β the danger comes specifically from how LOW the body's resistance becomes when wet (moisture provides a much easier path for current), which is exactly why the same voltage produces a far larger, more dangerous current under those conditions.
Real-Life Example
Why bathrooms have special electrical safety requirements
Building codes require bathrooms to use special ground-fault circuit interrupter (GFCI) outlets and keep switches away from water sources.
Wet skin dramatically lowers the body's resistance, so even household voltage becomes far more dangerous near water β these safety requirements exist specifically because of this relationship between resistance and shock current.
Practice
The same person, now with dry skin (resistance 100000 ohms), touches the same 230 V circuit. Find the shock current, in mA.
MediumCommon mistake
Assuming a given voltage is either "safe" or "dangerous" in isolation β the actual danger depends on the CURRENT that flows, which depends just as much on the body's resistance (wet versus dry) as on the voltage itself.
Quick Review
- I = V/R β a direct application of Ohm's law to the human body.
- Wet skin has far lower resistance than dry skin, producing much more dangerous shock currents.
- The basis for practices like GFCI outlets and avoiding electricity near water.