Physics Core/AP 1 and 2

Homework

# Physics 16: 1-6 Electrical Charge

## Homework

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 16: Sections 1 to 6.

##### Study Points
• Section 1: Charge, like mass, is a conserved property of matter: it cannot be created or destroyed, but it can change distribution. Like charges repel one another; unlike charges attract one another. When we add charge up, we have to take the sign of the charge into account: negative charge cancels positive charge.
• Section 2: Charge in the atom is concentrated in protons, where it is positive, and electrons, where it is negative. The other massive particle found in atoms, the neutron, gets its name because it is electrically neutral.
• Section3 : Substances in which electrons or charged particles can move freely are conductors; where charges cannot move freely, the effects of electrical charge are blocked.
• Section 4: If a conductor is placed near a charge source, the electrons in the conductor will rearrange themselves, moving toward a positive charge and away from a negative charge. Even though the substance is isolated and no electrons move from one substance to another, locally-charged areas form. This phenomena is induction.
• Section 5: The rate at which particles are accelerated by nearby charges is given by Coulomb's law. If a point charge q is placed near a static charge Q, q will experience an electrical force equal to kQq/r2. If Q*q is negative, the force is attractive. If Q*q is positive, the force is repulsive.
• Section 6: Forces due to individual point charges can be added, just as gravitational forces due to individual point masses can be added, using vector mathematics.

### Key Equations

• Coulomb's law
• The constant k and permittivity of free space ε0:

### Web Lecture

Read the following weblecture before chat: Electric Charge and Static Fields

### Study Activity

Use the simulation below to explore electric charge on the "macro scale", where large object have a net charge. Vary charges on objects #1 and #2 and then vary the distances between charges to see how force magnitude changes. Repeat your observations to become familiar with how charges on the atomic scale create forces to hold electrons and protons together in atoms, and atoms together in molecules.

Physics simulation Java Applets are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.

### Chat Preparation Activities

• Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
• Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

### Chapter Quiz

• The chapter quiz is not yet due.

### Lab Work

If you want lab credit for this course, you must complete at least 12 labs (honors course) or 18 labs (AP students). One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!