 # Lecture in Electric Charge and Electric Field

(Last Updated On: December 8, 2017)

### Lesson Objectives – the students should be able to:

• State from memory the magnitude and sign of the charge on an electron and proton and also state the mass of each particle.
• Apply Coulomb’s law to determine the magnitude of the electrical force between point charges separated by a distance r and state whether the force will be one of attraction or repulsion.
• State from memory the law of conservation of charge.
• Distinguish between an insulator, a conductor, and a semi conductor and give examples of each.
• Explain the concept of electric field and determine the resultant electric field at a point some distance from two or more point charges.
• Determine the magnitude and direction of the electric force on a charged particle placed in an electric field.
• Sketch the electric field pattern in the region between charged objects.
• Use Gauss’s law to determine the magnitude of the electric field in problems where static electric charge is distributed on a surface which is simple and symmetrical.
• Could understand Static Electricity; Electric Charge and Its Conservation
• Solving Problems Involving Coulomb’s Law and Vectors
• Learn Electric Forces in Molecular Biology: DNA Structure and Replication
• Understand Photocopy Machines and Computer Printers Use Electrostatics

### Summary of Chapter 16

• Two kinds of electric charge – positive and negative
• Charge is conserved
• Charge on electron:
• Conductors: electrons free to move
• Insulators: nonconductors
• Charge is quantized in units of e
• Objects can be charged by conduction or induction
• Coulomb’s law:
• Electric field is force per unit charge:
• Electric field of a point charge:
• Electric field can be represented by electric field lines
• Static electric field inside conductor is zero; surface field is perpendicular to surface
• Electric flux:
• Gauss’s law:

### Units of Chapter 16 – Keywords

• Static Electricity; Electric Charge and Its Conservation
• Electric Charge in the Atom
• Insulators and Conductors
• Induced Charge; the Electroscope
• Coulomb’s Law
• Solving Problems Involving Coulomb’s Law and Vectors
• The Electric Field
• Field Lines
• Electric Fields and Conductors
• Gauss’s Law
• Electric Forces in Molecular Biology: DNA Structure and Replication
• Photocopy Machines and Computer Printers Use Electrostatics