What a learner can do afterwards
- Explains a charged object in terms of electrons moved, never protons
- Draws field lines around a positive and a negative charge with arrows the right way
- Links a large potential difference across a small gap to a strong field and a spark, and gives an everyday example
1 · Read
Remember the balloon that lifted your hair. Rubbing moves electrons from one surface to the other, never protons. The surface that gains electrons turns negative and the one that loses them turns positive, and like charges push apart while opposite charges pull together. None is created: the charge only separates into matching pairs.
An electric field is the invisible zone of influence around any charge. Draw it with lines that start on positive charges and end on negative ones. Crowded lines mean a strong field, spread out lines mean a weak one, and lines never cross.
A big voltage across a small gap makes a fierce field, and air itself can break down and conduct. The shock touching a car door is charge from the drive rushing across a tiny air gap. Lightning is the same story written huge across the sky.
Insulators trap shifted charge in place for minutes, which is why a rubbed balloon sticks to a wall. Metals let the imbalance flow away at once, so they rarely show static. Static tricks always use plastic, glass, or cloth, never bare metal.
Electrons move, fields point away from positive, and a fierce field across a gap makes a spark.
The rewritten readings were written for this dataset.
More to read
Transferring charge by rubbing
In common static-electricity examples, rubbing transfers electrons between materials. Protons remain in their nuclei. Gaining electrons gives a negative charge; losing them gives an equally large positive charge. The total charge is unchanged.
Charges of the same sign repel; different signs attract. A charged balloon or comb can also rearrange charges in a neutral wall or hair, producing attraction. Small amounts of charge can exert noticeable forces.
Reading an electric field
An electric field describes the electrical force a charge would experience at each position. Field-line arrows give the direction for a positive test charge. Lines point away from positive charges and toward negative charges; some extend to infinity. Closer spacing represents greater field strength.
Lines cannot intersect because the field has one direction at a point. At a conductor's surface in electrostatic equilibrium, they are perpendicular.
From charge imbalance to a spark
An object is electrically neutral when its positive and negative charges balance. An imbalance produces static charge; rubbing is one way to create it. Metals allow charge to redistribute, but it needs a conducting route to escape. Insulators can retain localized charge for minutes.
A large voltage over a narrow gap produces a strong field that can make air conduct. A car-door spark happens when accumulated charge crosses such a gap. Lightning is an electrical discharge on a much larger scale.
Explore more
2 · Watch
En anglaisTake it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.