When electricity flows through an object, moving electrons collide with the object’s atoms and transfer energy to them. This produces several effects simultaneously: the object heats up, a magnetic field forms around it, and if the object is a liquid solution, chemical reactions can occur at its surfaces. The exact mix of effects depends on what the object is made of and how much current passes through it.
The Object Heats Up
The most universal effect is heat. As electrons move through a material, they bump into atoms along the way. Each collision transfers a tiny amount of energy to those atoms, making them vibrate faster. Faster atomic vibration is what we experience as heat. This process, called Joule heating, happens in every material that conducts electricity, from a copper wire to a toaster coil to a human body.
The amount of heat generated depends on two things: how much current is flowing and how much the material resists that flow. Specifically, the heat produced rises with the square of the current. Double the current and you get four times the heat. This is why high-current appliances like space heaters and electric stoves get so hot, while the wiring behind your walls stays cool carrying smaller currents.
In a standard incandescent light bulb, this heating effect is pushed to an extreme. The thin tungsten filament reaches roughly 2,550°C (about 4,600°F). At that temperature, the filament glows white-hot, producing visible light. Only about 5 percent of the electrical energy actually becomes light, though. The rest radiates away as heat, which is why incandescent bulbs are so inefficient and warm to the touch.
A Magnetic Field Forms Around It
Any time electricity flows through an object, a magnetic field appears in the space surrounding it. The field forms in circular loops around the path of the current. If you imagine wrapping your right hand around a wire with your thumb pointing in the direction the current flows, your fingers curl in the direction of the magnetic field. This relationship between current direction and field orientation holds true for any shape of conductor.
This effect is the basis of electromagnets, electric motors, and transformers. A single wire produces a relatively weak field, but coiling the wire into many loops concentrates the effect. The total field is the sum of the contributions from every segment of the current path, so more loops and more current mean a stronger magnet. When you turn the current off, the magnetic field disappears.
Chemical Changes in Liquids
When electricity passes through a liquid solution containing dissolved ions (charged atoms or molecules), it drives chemical reactions at the surfaces where the electrodes meet the liquid. This process is called electrolysis. Positively charged ions migrate toward the negative electrode, pick up electrons, and transform into new substances. Negatively charged ions travel to the positive electrode, release electrons, and undergo their own transformation.
The results can be dramatic. Passing current through water splits it into hydrogen gas and oxygen gas. Running current through molten table salt produces pure sodium metal and chlorine gas. Electrolysis of a saltwater solution yields sodium hydroxide and chlorine gas, both valuable industrial chemicals. This chemical effect only occurs in liquids and solutions, not in solid conductors like metal wires, because the ions need to be free to move.
Why Some Objects Resist More Than Others
Not all objects respond to electricity in the same way, and the key difference is resistance. Every material has an intrinsic property called resistivity that determines how easily electrons can flow through it. The gap between good conductors and good insulators is staggeringly large.
Copper, the standard choice for electrical wiring, has a resistivity of about 0.0000000168 ohm-meters. Silver is slightly better. Aluminum is close behind. These metals have outer electrons that move freely between atoms, creating an easy path for current. At the other extreme, hard rubber has a resistivity around 10,000,000,000,000 ohm-meters, roughly a thousand trillion trillion times higher than copper. Glass, dry wood, and Teflon fall in a similar range. In these materials, electrons are tightly bound to their atoms and barely move at all.
This is why the same voltage that sends a large current through a copper wire produces essentially zero current through a rubber glove. The material’s resistance determines how much current flows, which in turn determines how strong the heating, magnetic, and chemical effects will be.
What Happens When the Object Is a Human Body
The human body conducts electricity because it’s full of salty water, which contains mobile ions. The effects follow the same principles as any other conductor, but with biological consequences that escalate quickly with increasing current.
At about 1 milliamp of alternating current (one one-thousandth of an amp), a person can barely feel a tingle. At 10 to 16 milliamps, muscles begin contracting involuntarily, and you may lose the ability to let go of whatever is delivering the shock. At 20 milliamps, the muscles that control breathing can lock up, making it impossible to inhale. At 100 milliamps, about a tenth of an amp, the electrical signal can override the heart’s natural rhythm and cause ventricular fibrillation, a chaotic quivering that stops the heart from pumping blood.
For context, a standard household outlet can deliver far more than 100 milliamps. What limits the current through your body is your skin’s resistance. Dry skin provides a significant barrier. But wet or broken skin drops that resistance dramatically, allowing much more current to reach internal tissues. This is why electrical accidents near water are especially dangerous.
All These Effects Happen at Once
It’s worth noting that these effects aren’t alternatives. They happen simultaneously whenever current flows. A wire powering a lamp heats up, generates a magnetic field, and (if it passes through any liquid junction) can trigger chemical changes all at the same time. Which effect dominates depends on the situation. In a toaster, heating is the point. In an electric motor, the magnetic effect does the useful work. In an electroplating bath, the chemical effect is what matters. But the others are always there in the background, sometimes as useful byproducts, sometimes as waste, and sometimes as hazards.