Electric Charges and Fields: A High School Physics Introduction, Lecture notes of Law

Download Electric Charges and Fields: A High School Physics Introduction and more Lecture notes Law in PDF only on Docsity!

Electric Charges and Fields

Chapter 22

Interaction of Charges

• Opposite charges attract (positive to negative)
• Like charges repel each other (positive to positive OR negative to negative)

Interaction of Charges

• If a balloon is known to have a negative charge and is attracted to another balloon, what must the charge on the second balloon be?
• If I put a metal rod which I do not know the charge of next to a negatively charged sphere and the sphere rolls away from it what can I infer the charge of the rod is?
• Two balls are interacting, one has a charge of - 3 and one is neutral. Which experiences a greater electrostatic force?

The two fundamental charge interactions are:

• oppositely charged objects attract
• like charged objects repel.

These mutual interactions resulted in an electrical force between the

two charged objects.

This force is MUCH greater than the force of gravity!

Charge Interactions are Forces

Coulomb's Law

The magnitude of the electrostatic force of attraction or repulsion between two charges is:

• directly proportional to the product of the magnitudes of charges If either charge goes up, the total force goes up

Coulomb's Law

The magnitude of the electrostatic force of attraction or repulsion between two charges is:

• inversely proportional to the square of the distance between them. F d

Practice

Two charges that are 2 meters apart repel each other with a force of 2x

• 5 newton. If the distance between the charges is decreased to 1 meter, what will the force of repulsion be?

Practice

A repulsive electrostatic force of magnitude F exists between two metal spheres having identical charge q. The distance between their two centers is r. Which combination of changes would produce no change in the electrostatic force between the two spheres? 1.doubling q on one sphere while doubling r 2.doubling q on both spheres while doubling r 3.doubling q on one sphere while halving r 4.doubling q on both spheres while halving r

• Suppose that two point charges, each with a charge of +1.00 Coulomb are separated by a distance of 1.00 meter. Determine the magnitude and direction of the electrical force of repulsion between them. Practice

What is an Electric Field?

• How can an apple reach across space and falls toward Earth?
• The Earth creates a Gravitational field. Other masses in that field would feel its effect in the space. Whether a mass object enters that space or not, the gravitational field exists.

Drawing an Electric Field Rules

Electric Field Lines

• Lines are directed away from positively charged source charges and toward negatively charged source charges.
• The closer lines near the charge indicating stronger field.

• The electric field is ___________________ at locations closest to the surface of the charge and least at locations further from the surface of the charge. greatest

3. Electric field lines should _____________________.

• Every single location in space has its own electric field strength and direction associated with it; consequently, the lines representing the field cannot cross each other at any given location in space. never cross