Circuits Objective: I will understand how electricity flows in a simple circuit.

What is Matter? All matter is made up of small particles called atoms. Atoms have 3 parts: Proton (positive) and neutron (neutral) which makes up the center or the nucleus Electrons (negative) which orbit around the nucleus

Everything in the universe is made of some combination of the 118 elements. Each element is unique because it has a different number of protons, neutrons, and electrons

Moving Electrons Normally, atoms have an equal number of protons (positive) and electrons (negative), and therefore the opposite charges cancel each other out causing the atom to have a neutral charge. Electrons orbit the atom, and so can get lost. Atoms may have too few electrons or too many at any time. Atoms with an imbalance of electrons are said to be “charged.” An atom with missing electrons is positively charged. An atom with extra electrons is negatively charged.

Just like magnets, oppositely charged atoms attract each other!

Moving Charges Atoms with opposite charges are always looking to exchange electrons and return to their normal, uncharged state. Electrical conductors are materials in which charges (electrons) can move easily. Most metals are good conductors. Metal is often used to make things that should carry a charge (Ex. Wires)

Electrical insulators are materials in which charges (electrons) cannot move easily. Plastic, rubber, glass, wood, and air are all good insulators. These materials are used to make things that should not carry a charge (ex. Wire coating) Which number represents the insulator here?

What is Electricity? An electric current is the rate at which charges pass a given point. The higher the current, the greater the number of charges passing a certain point each second. Electric current is measured in a unit called amperes, usually shortened to amps.

Moving Charges When you flip the light switch, do electrons travel from there to the light instantly? No, the electrons transfer from atom to atom immediately, so the effect only seems instant. It’s similar to dominoes.

Did you know? Electricity only seems to move quickly because all the charges move at the same time. A single electron could take up to an hour to move only 1 meter inside a wire!

Review In your own words, describe electricity and how it works as you would to a younger student. If you cannot do so, please ask questions!

Two Types of Current Direct Current – Charges always flow in the same direction Alternating Current – Charges continually shift from flowing in one direction to flowing in the reverse direction

Voltage If you are on your bike at the top of a hill, you know you can roll ot the bottom. You can do so because of the difference in height between the two points. The “hill” that causes charges in a circuit to move is called voltage. Voltage is the potential difference between two points in a circuit. Voltage is measured in volts.

Voltage Voltage is a measure of how much force is present to move electrons (charge) between two points. Think of voltage as similar to pressure in a water pipe that makes the water flow when you turn on the tap. The higher the voltage is, the more energy is released per charge.

What is a Circuit? Imagine a roller coaster. You speed around the track, but you always end up where you started. The coaster follows a fixed path. This kind of closed path is the same as a circuit.

Electric Circuit An electric circuit is a complete, closed path through which electric charges flow.

Parts of an Electric Circuit Energy Source – Battery, generator, etc. Wires – Carrying the electricity Load – Light bulb, radio, etc.

If the path of the circuit is broken, for example by opening the switch, the current will no longer flow.

Circuits Around You How many circuits do you see around you? Can a circuit have more than one load?

Series Circuits In a series circuit, all the parts are connected in a single loop. There is only one path for the charges to follow, so the charges must flow through each part of the circuit. What are the benefits and drawbacks of a series circuit? Hint: think about your Christmas tree lights

Parallel Circuits In a parallel circuit, charges have more than one path on which they can travel. Unlike in a series circuit, in a parallel circuit the loads do not have the same current. Because of this, each load can use the full voltage of the battery instead of having to share. Also, now if one load fails, the rest will continue to work. Would you use a parallel or series circuit for the lights in your home?

Circuit Failure Broken wires or water may cause a short circuit. In a short circuit, charges do not go through one or more loads in the circuit. The resistance decreases, and current increases. Wires heat up, and the circuit could fail. The wires could even get hot enough to start a fire. Fuses and circuit breakers help prevent electrical fires.

Fuses A fuse has a thin strip of metal. The charges in the circuit flow through the strip. If the current gets too high, the metal strip melts, and the circuit is broken so electricity no longer flows.

Circuit Breaker A circuit breaker is a switch that automatically opens if a current is too high. A strip of metal in the breaker warms up, bends, and opens the switch, which opens the circuit. Charges then stop flowing. Open circuit breakers can be closed by flipping a switch after the problem has been fixed.

Review What are the similarities and differences between parallel and series circuits? What dangers do circuits present in our homes and buildings?

Will this circuit work?