Electricity and circuits

Electricity and Circuits

Physical ScienceMrs. Neistadt

*Electricity

• *What is electricity?*Electricity is a general term for anything that involves an electrical charge.

• *What causes an electrical charge?*An electrical charge is caused by an imbalance in positive or negative charges.

Electricity and Circuits• *What is an electrical circuit?• **An electric circuit is something that

provides a path through which electricity travels.

• We use electrical circuits everyday in all of our electrical appliances.

What exactly is electricity? How does it work?

What is electricity?• *Electricity usually means the flow of an

electric current in wires, motors, light bulbs, and other devices.

• *Electricity is like water, except it flows through solid metal so we can’t usually see it.

• *Just like water, electric current can travel over great distances.

What are examples of an electric circuit?

• An electric circuit is something that provides a path through which electricity travels.

*Some electric circuits exist in the natural world:– *Nerves in your body create electric circuits– *Lightning, clouds, and planet Earth form an electric circuit

*Some Man-made electric circuits are::– *Wiring that lights your house– *Car battery, ignition switch, and starter in a car

1. The nervous system in the

body acts like an electric circuit.

A. YesB. No

2. Which of these is NOT an electric circuit?

A. The wiring the lights your house.

B. Lightning, clouds, planet EarthC. Water flowing through pipes

in a house.[Default][MC Any][MC All]

Electric currents = water pipes

• Electric circuits are similar to pipes and hoses for water. – The big difference is that when you cut a hose, the

water flows out, but when you cut a wire, electricity stops flowing.

*Two types of Circuits

• *Closed Circuits: current flows• *Open circuits: no current flows• *The most common problem in circuits is an

unintentional break in the circuit.

3. When a current is broken, where does the electricity go?

A. It spills out onto the ground.B. The current stops, electrical currents only

flow in closed circuits.C. It floats off into space.[Default][MC Any][MC All]

4. An open circuit is a circuit with no breaks in

it.

A. TrueB. False

5. A closed circuit turns a light off.

A. TrueB. False

Switches and Circuits• *A complete path through wire is

needed for electricity to work. • *A switch works by breaking or

completing the circuit path.• *When the switch is on: the circuit path

is complete.• *When the switch is off: the circuit path

is broken.

*Circuit diagrams make drawing circuits much easier.

Closed Circuits = Electricity Flow

Open Circuit = No Flow

Circuit Diagram Symbols

Answer in your own words:1. On your paper, create a drawing of an electric

circuit using the symbols found on page 109.2. What is a closed circuit? 3. What is an open circuit? 4. If you compare an electrical circuit to a system that

carries water, what would the water pipes represent?

Summarize:Now that you’ve learned a little more about electrical

circuits, answer the original question again: What is an electrical circuit? Answer in your own words.

Electricity and CircuitsPart II

Physical ScienceMrs. Neistadt

Bellwork Questions:

1. What is Static Electricity?2. When have you experienced static

electricity?

**Static Electricity- a build up of either positive or negative charge; consists of isolated motionless charges, like those produced by friction.Examples: brushing hair; cat fur; socks on carpet; clothes from the dryer…

Review Questions:

1. If you compare an electrical circuit to a system that carries water, what would the water pipes represent?

2. Is a closed circuit on or off?

3. A circuit with the switch turned to the OFF position or a circuit with any break is called an open or closed circuit?

History

• The study and using of electricity is relatively new: scientists only began understanding electricity in the late 1800s.

• Scientists first believed electricity was caused by two fluids in an object.

• They now know that it is not fluid, but positive and negative charges of an electrical energy in an object.

More history• *Electric charge is a fundamental property of

matter that comes in two forms.

• *Benjamin Franklin was one of the scientists who discovered this fact.

• *Ben Franklin also named the two forms of charges positive and negative.

Static Cling Anyone?

• If objects can have a positive or a negative charge, what happens when there is a buildup of these charges?

• *When an object carries extra positive or negative charges, we say it is electrically charged.

6. Benjamin Franklin thought electricity

was caused by a certain fluid present in

an object.A. TrueB. False

Charges

• *Like charges (+,+) (-,-) repel each other• *Unlike charges (+,-) attract• *An object that has equal positive and

negative charges is called: electrically neutral

• *This property of matter, Charge, gives rise to both electricity and magnetism.

Practice Questions:

1. Positive electric charges:a. attract both positive charges and negative chargesb. Repel both positive charges and negative chargesc. Attract positive charges and repel negative chargesd. Repel positive charges and attract negative charges

2. Electric charge is:a. Caused by two fluids, as described by Benjamin Franklinb. Present in metals onlyc. A fundamental property of matter that comes in two formsd. Found only in non-living material

What is happening in the picture?

This picture was taken after the girl had rubbed the balloons over her hair and then pulled them away. An atom contains protons at the center and electrons which surround it on the outside. The number of

protons in an atom can't change, but electrons can either be added or taken away. This causes the atom to have a positive or negative charge. In this case, electrons were transferred from the balloon

to her hair, giving the balloon a positive charge and her hair a negative charge. This is due to the Conservation of Electric Charge, which says that electric charge can't be created or destroyed. Since

positive and negative charges attract, her hair is attracted to the balloon and sticks to it.

Balloon QuestionsAnswer on your paper:

1. How did the balloons get stuck to the board?2. What did rubbing do to the balloons?3. Why do you think balloons will stick better

on a very cold winter day than on a rainy day?

4. Can the balloons stick to the walls forever?

Answer on your paper:

• Complete Concept Review Questions • #1-11 on page 115 of your text• Please turn in