Understand the fundamental nature of charge, including its conservation and quantization.
Preview · progress not saved — Chapter 1 is free
Explains polarity, conductors vs insulators, and basic charge properties.
Have you ever felt a shock from a car door or seen lightning? These phenomena are due to electric charge. When certain insulating materials are rubbed together (like a glass rod and silk), they transfer charge, creating static electricity.
Historically, Benjamin Franklin named the two resulting states of electrification positive and negative. Like charges repel, and unlike charges attract.
Visual showing electron transfer between glass rod and silk.
Rubbing an insulator transfers electrons, creating opposite polarities on each material. Charge is conserved; no new charge is created.
Formula card for q = ne.
Calculates time to transfer 1 Coulomb if 10^9 electrons move per second.
Problem
If electrons move out of a body to another body every second, how much time is required to get a total charge of C on the other body?
Given:
Calculates total positive and negative charge in 250g of water.
Problem
How much positive and negative charge is there in a cup of water?
Given:
Calculate the total charge of a given number of particles.
To find the total positive charge in 1 mole of Helium gas, we first determine the number of atoms. By definition, one mole of Helium contains approximately atoms. Each Helium atom contains exactly protons in its nucleus.
The magnitude of the positive charge contributed by a single proton is the elementary charge , which is . We can find the total positive charge by multiplying the total number of atoms by the number of protons per atom and the elementary charge.
Total positive charge = .
Evaluating this expression gives a total positive charge of roughly .