Conductors, Insulators, and Charging Basics

Conductors allow electricity to pass through them easily.
Insulators resist the flow of electricity.
Semiconductors have resistance between conductors and insulators.
When charging a conductor, the charge is distributed across its surface; When charging an insulator, the charge stays in the same place.

Detects charges on a body.
Consists of a vertical metal rod with two leaves attached at the bottom.
The leaves diverge when a charged object touches the rod, indicating the amount of charge.

Materials gain charges by gaining or losing electrons.
Rubbing glass with silk makes the rod positively charged and the silk negatively charged.
Rubbing plastic with fur makes the rod negatively charged and the fur positively charged.
This transfer of charge redistributes existing charges, not creating new ones.

All charges are integral multiples of a basic unit of charge, e.
Any body's charge (q) is q = ne*, with n being an integer.
e is the charge of a proton (+e) or electron (-e).
The basic unit of charge in the SI system is the coulomb (C).
One coulomb is one ampere flowing through a conductor for one second.
e = 1.602192 × 10^-19 C.
A body with n₁ electrons and n₂ protons has a total charge of (n₂ - n₁)e.
While the basic unit e is small, at larger scales, the quantized nature of charge is not apparent.

Static electricity is the study of forces, fields, and potentials resulting from stationary charges .
Amber rubbed with wool or silk attracts light objects.
The word "electricity" comes from the Greek word for amber.

Rubbing two glass rods with wool or silk makes them repel each other.
The glass rods attract the wool.
Rubbing two plastic rods with cat's fur makes them repel each other and attract the fur.
The plastic rods attract glass rods and repel the silk or wool that was used to rub the glass rods.
These observations indicate the existence of two types of electric charges: like charges repel, unlike charges attract.

Contact between charged objects neutralizes their charges, nullifying their effects.

The experiment illustrates the transfer of electrons from a body.
It explores what happens in isolated bodies when one body gains or loses charge.

Coulomb's law is a fundamental law of physics that quantifies the electrostatic interaction between electrically charged particles.
The force between two point charges is called the electrostatic force.
Coulomb's law is expressed as F = k|q₁q₂|/r²:
- F is the force
- k = 1/(4πε₀) is a constant
- q₁ and q₂ are the magnitudes of the charges
- r is the distance between the charges
The direction of the force is along a vector pointing from the first charge to the second charge.
The force is attractive if the charges have opposite signs and repulsive if they have the same sign.

Coulomb was a French physicist.
He invented the torsion balance to measure electrostatic forces between charged spheres.
He discovered Coulomb's law in 1785.

Coulomb used a torsion balance to measure electrostatic forces.
The experiments involved:
- Initially unknown charges on spheres: Coulomb developed a method to determine the charges.
- Contact Charging: Transferring charge by contacting spheres led to doubling the charge, and repeated contact enabled creation of different charged pairs.
- Varying Distance: For a fixed charge pair, Coulomb varied the distance and measured the force.
- Varying Charges: For a fixed distance, Coulomb varied the charges and measured the forces.
Comparing the results helped determine the inverse square law relationship.

The example shows how a large amount of charge can be accumulated over a long time due to the transfer of small amounts of charge.
It calculates the time required for 1C charge to accumulate from the transfer of 10⁹ electrons per second.

The example determines the positive and negative charge in a cup of water.
It utilizes Avogadro's number and the composition of water to calculate the total charge.

The example compares the strength of electric and gravitational forces between two charges or masses.
It calculates the ratio of electric force to gravitational force for:
- An electron and a proton.
- Two protons.
It highlights the significantly larger magnitude of electric force compared to gravitational force for charged particles.

This example likely presents a scenario involving two charged metallic spheres suspended by threads.
Information about the distance between the spheres and their charges is given.
The example likely involves calculations or analysis related to electrostatic forces and interactions.