Mechanical and Electrical Energy

Session #16

WARM UP

Looking at the picture on the right.

List as many types of energy that you can see.

Explain how those types work together to create electricity.

http://www.pbs.org/tesla/ins/niagara.html

Warm Up DiscussionWhen water trapped behind a dam is channeled to push on the blades of a turbine, the potential energy of the still water changes form.

When the water starts to move, the potential energy becomes kinetic energy.

When the turbine starts to spin, the kinetic energy becomes mechanical energy.

The spinning motion of the turbine is used to rotate a coil of copper wire between two opposite magnetic poles. This starts electrons moving down the wire. When the coil of copper wire rotates past the North magnetic pole, the electrons move down the wire in one direction. When the coil rotates past the South magnetic pole, the electrons reverse direction. This back-and-forth flow of electricity through a wire is called alternating current-otherwise known as AC.

Homework:Thermal Expansion and ContractionThermal Expansion: All gases, many

liquids and most solids expand when the temperature is increased. Why?

Thermal Contraction: As an object cools, the object contracts, or gets smaller. Why?

Why do we need to know this:

Expansion Joint on a bridge

So that it doesn’t do this:

Expansion joint strips in bridges allow for the bridge to expand in hot weather and not break. These same joint strips allow for the bridge to contract in cold weather and not break.

http://app.discoveryeducation.com/search?Ntt=conductors+insulators1A Only

THIS IS THE LAW OF CONSERVATIONOF ENERGY

Energy can neither be created nor destroyed; it can be changed from one form to another.

Mechanical Energy

Energy associated with the motion of an object.

ChewingSoundFrog Dancing

Remember: Potential and Kinetic energy

Mechanical Energy Recap

Mechanical energy is the energy that is possessed by an object due to its motion or due to its position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position).

A drawn bow possesses mechanical energy due to its stretched position (elastic potential energy).

An object that possesses mechanical energy is able to do work. In fact, mechanical energy is often defined as the ability to do work.

So, an object that possesses mechanical energy - whether it is in the form of potential energy or kinetic energy - is able to do work.

Electrical EnergyMovement of electrons (electrical

charges) that produce electricity.

Static ShockLightningComputers/

TVs/RadiosLights

Electrical Energy

Electrical energy is the movement of electrons between atoms. Lightning and static electricity are examples of electrical energy that occur naturally.

Science hasn't found a way to use natural forms of electrical energy, like lightning. Instead, we use different energy sources to create electrical energy by using generators and turbines.

A battery produces electricity using two different metals in a chemical solution. A chemical reaction between the metals and the chemicals frees more electrons in one metal than in the other.

The end that frees more electrons develops a positive charge and the other end develops a negative charge. If a wire is attached from one end of the battery to the other, electrons flow through the wire to balance the electrical charge.

A load is a device that does work or performs a job. If a load –– such as a light bulb –– is placed along the wire, the electricity can do work as it flows through the wire. Electrons flow from the negative end of the battery through the wire to the light bulb. The electricity flows through the wire in the light bulb and back to the positive end of the battery.

Electricity travels in closed loops, or circuits. It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we flip on a light switch, we close a circuit. The electricity flows from an electric wire, through the light bulb, and back out another wire.

Is this an open or closed circuit?

Scribble Machine

You will receive the following:

MotorBattery pack2 sets of alligator clipsPaperMarker

You will also receive the following:

6 Paper Clips4 Popsicle Sticks4 Rubber Bands4 Pipe Cleaners1 Plastic Cup1 Index Card12” of Masking TapeBlob of Play Doh

Scribble Machine:

Design a plan with your group to make a machine that draws (scribbles) automatically.

Test your model.Sketch and label your model before class

is over.Answer the Questions on your Lab Sheet

for Homework.