Positive
Protons carry one positive elementary charge. Like positive charges repel one another.
Electricity · Charge & fields
What is
charge?
Charge is a fundamental property of matter. Just as mass tells us how something responds to gravity, electric charge tells us how it creates and responds to electric fields.
01 · The property
Charge is something particles have.
We do not currently explain charge in terms of a smaller mechanism—it is one of nature’s basic properties. We describe it by what it does.
Negative
Electrons carry one negative elementary charge. Opposite charges attract.
Neutral
Equal positive and negative charge cancels overall, though the charges are still present.
Charge is quantized. It comes in discrete units. An electron carries −e and a proton carries +e, where e is about 1.602 × 10−19 coulombs.
Charge is conserved. In ordinary processes it can move between objects, but the total amount of charge does not appear or vanish.
02 · Try it
Charges push and pull
through a field.
Every charge changes the space around it. Another charge placed in that space experiences a force. That “condition of space” is the electric field.
Charge interaction
Choose the two charges and change their separation. Electric force weakens with the square of distance.
+−
Inverse-square law
Double the distance and the force becomes one quarter as strong.
03 · From charge to electricity
Most matter has charge.
Conductors let some of it move.
In a metal, some electrons are not bound to one atom. They form a mobile “sea” throughout the material. Without an electric field their thermal motion is random, so there is no net current.
Connect a battery into a closed circuit and it establishes an electric field through the conductor. The mobile charges gain a tiny net drift on top of their random motion. That organized drift is current.
04 · A better mental model
Electricity is charge
and fields.
Charge
The property that creates and responds to electrical effects.
Field
The influence a charge creates throughout the space around it.
Force
The push or pull a charge experiences when placed in a field.
Next lesson
What gets charge moving?
Now connect fields to voltage, current, and resistance.
Continue to circuit basics →