1. Foundations of Physical Science
Unit 3: Electricity and Magnetism

2. Chapter 6: Electricity and Electric Circuits
6.1 What is a Circuit?
6.2 Charge

3. Learning Goals Build simple circuits. Trace circuit paths.
Interpret the electric symbols for battery, bulb, wire, and switch.
Draw a circuit diagram of a real circuit.
Explain why electrical symbols and circuit diagrams are useful.
Explain how a switch works.
Identify open and closed circuits.
Charge pieces of tape and observe their interactions with an electroscope.
Identify electric charge as the property of matter responsible for electricity.
List the two forms of electric charge.
Describe the forces electric charges exert on each other.
Describe how lightning forms.

4. Vocabulary circuit diagram closed circuit coulomb electric circuits
electrically charged
electric charge
electrically neutral
electroscope
electrical symbols
natural world
negative charge
open circuit
positive charge
static electricity
versorium

5. What is a Circuit?
Something that provides a path through which electricity travels
Electricity: the flow of electric current in wires, motors, light bulbs, and other devices
Electric current: flow through solid metal; can carry energy over great distances
Can be powerful and dangerous!

6. Circuits Are All Around Us!
Wiring that lights your house
Nerves in your body
Lightning, clouds, and the planet Earth
Car battery, ignition switch, and starter
Electric circuits are like water pipes and hoses, except electricity cannot flow if a wire is cut (but water can!)
Switches turn circuits on and off

7. Circuit Diagrams
Circuit are made up of wires, electrical parts (batteries, light bulbs, motors, or switches)
Circuit diagrams are used as a shorthand method to describe a real circuit
Resistor: an electrical component that uses energy (example: light bulbs)

8. Circuit Diagrams

10. Open and Closed Circuits
Open circuit: a circuit with a switch turned to the off position of a circuit with any break in it
Closed circuit: a circuit with the switch(es) turned to the on position, without any breaks in the wire. If attached to a light bulb, the light will be on!
Short circuit: an accidental extra path for current to flow

12. Charge Electric charge is a fundamental property of matter.
Flows through a circuit
There are two types of charge:
positive
negative

13. Charge
The terms positive and negative to describe the opposite kinds of charge were first used by Benjamin Franklin ( ).
In 1733, French scientist Charles DuFay had published a book describing how like charges repel and unlike charges attract.

14. Atoms Same number of electrons as protons Ion: a charged atom
Positive ion: lost electrons
Negative ion: gained electrons

15. Conservation of Charge
No electrons are created or destroyed
They are transferred from one material to another
Charge is conserved

17. Example
If you walk across a rug and scuff electrons from your feet, are you negatively or positively charged?
You have fewer electrons and are thus positively charged (the rug is negatively charged)

18. The Coulomb The unit of electric charge (C)
Named after Charles-Augustin de Coulomb, a French physicist

19. The Electroscope Tool used to measure charge in objects
Versorium: the first electrical instrument
The earliest version of today’s electroscope

20. Coulomb’s Law Electrical force has a pattern like gravitational force
Discovered by Charles Coulomb in the 1700s
Like charges: repelling force
Unlike charges: attractive force

22. Coulomb's Law in Summary
Newton’s law of gravitation for masses is similar to Coulomb's law for electrically-charged bodies
The important difference: electrical forces may be either attractive or repulsive, whereas gravitational forces are only attractive