Electrical Principles and Technologies

Unit D

Key TermsKey TermsUse the spaces below to define the key terms in your own words.Use the spaces below to define the key terms in your own words.

1.1Key Terms Textbook Definition Drawing / In my own words

Static Electricity

Proton

Electron

Neutral

Charge Separation

Electrical Discharge

1.2Key Terms Textbook Definition Drawing / In my own words

Electrical Current

Amperes

Conductors

Circuit

Load

Voltage

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Electrical Energy

Volt

Voltmeter

1.3Key Terms Textbook Definition Drawing / In my own words

Short Circuit

Insulator

Fuse

Circuit Breaker

1.4Key Terms Textbook Definition Drawing / In my own words

Electrochemical Cell

Dry Cell

Electrolyte

Ion

Electrode

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Wet Cell

Primary Cell

Rechargeable (Secondary) Cell

Battery

Electrolysis

Electrochemistry

Electroplating

CCHAPTERHAPTER 1 – E 1 – ELECTRICALLECTRICAL ENERGYENERGY CANCAN BEBE TRANSFERREDTRANSFERRED ANDAND STOREDSTORED

1.1 – S1.1 – STATICTATIC E ELECTRICITYLECTRICITY

Static electricity is a ________________________ electric charge, usually caused by two objects having been _________________ together.

The explanation for static electricity starts with the atom itself. Recall from Unit B that the atom is made up of a ______________, which contains __________________ and neutrons, and _________________ whizzing around the nucleus. Electrons are __________________ charged particles, while protons are __________________ charged particles.

Electrical Charge

Most objects have ________________ amounts of positive and negative charge, which makes them __________________. However, sometimes there is more of one type of charged particle than another.

An object that has ________________ electrons than protons is ___________________ charged (-). An object that has ______________ protons than electrons is _____________________ charged (+). The object then has a build up of ______________ charge.

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According to modern theory, __________________ charges on solid materials are due to the movement of ___________________ from one object to another. Franklin’s experiment of rubbing amber with fur helped establish _________ that describe the ____________________ between charged and uncharged objects.

Laws of Electrical Charge

1. Unlike charges (opposites) ____________________2. Like charges __________________3. Charged objects ____________________ neutral objects

Charge Separation

Charge __________________ occurs when a _____________ object is brought close to a _______________ object. In the situation below:

The (___) particles attract the (___) particles of the neutral object.

The area closest to the (___) object then has a (___) charge which attracts the (___) object.

Electrical Discharge

Electrical discharge: Occurs when a static charge (________________) is built up in an object. The negative charge is _______________ to the _______________ charge of another object. That attraction

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causes the _________________ to ________ to the other object. Sometimes the static discharge is seen or felt as a __________.

Example:

Lightning

Van de Graaff Generators

A Van de Graaff generator creates large amounts of static electricity by using ____________________. A _______________ belt rubs on a piece of ______________ and transfers the charge to the sphere. The charge _____________ up on the sphere and ___________________ to you when you touch the sphere

Check and Reflect – Pg. 278

1. How does a proton differ from an electron?

2. What does it mean to be “statically charged?”

3. Explain how a Van de Graaff generator builds up a static charge.

4. What happens when like charges interact? What happens when unlike charges interact?

6. A neutral object contains no charge. Is this statement accurate? Explain.

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7. Why is a neutral object attracted to a charged object?

8. You bring a negatively charged rod close to some tiny pieces of plastic. Some of the pieces jump up to the rod, but as soon as they make contact, they immediately fly away from the rod. Explain.

9. Large trucks that carry flammable liquids often have a metal wire or chain that drags on the ground. Why?

1.2 – C1.2 – CURRENTURRENT E ELECTRICITYLECTRICITY

Static electricity is not __________________ for operating electrical devices, because they build up and then _____________.

Electrical Current – The steady ____________ of _______________ particles is an electrical current. Current Electricity – Electricity that flows continuously.

http://www.youtube.com/watch?v=fDvZOp9Oqro

Current electricity is the type that is used to power devices. Unlike static electricity, current electricity flows continuously as long as two conditions are met:

1. The flow of electrical current requires an _________________ ________________

2. There must a _________________ path or _______________ for the charged particles to pass through

Circuits

A circuit is the _________ that __________________ the flow of electricity

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If you compare electricity with water, this is like the water system in your house. The pipes and taps control the flow of water.

In most circuits, the path that _______________ take is simply a _____________________ ________. However, some circuits can include gases, fluids, etc. A ___________________ is anything that allows the flow of electrons.

Circuits generally include a __________________, an energy _______________ and a ___________. A __________ is a device used to _________________ electrical energy into another form of energy.

Amperes

Imagine a fast-flowing river. If you were to describe the current you might state the number of liters of water that flow past a certain point every minute.

Similarly, scientists describe electric current as the ______________ of ____________ that passes a point in a conducting wire in a given _____________. The symbol for current is I.

The rate at which an electrical current flows is measured in amperes (A). http://www.youtube.com/watch?v=EJeAuQ7pkpc

Voltage

Electrical energy is the energy _______________ by _____________ particles. Voltage is a measure of how _____________ electrical energy each charged particle _________________.

The higher the voltage, the greater the potential energy of each particle

The unit of voltage is the ___________ (V), named for Alessandro Volta.

The simplest way to measure voltage is by using a _______________________.

Check and Reflect – Pg. 283

1. What is electrical energy?

2. How does current electricity differ from static electricity?

3. How would you describe voltage?

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4. What are the unit for measuring a) current and b) voltage?

5. You require a high-current battery to start a large tractor. While shopping for this battery, should you be more concerned with the battery’s rating of volts or amps? Explain.

6. A wire carrying more electrons will transfer more energy than a wire carrying fewer electrons. Is this statement accurate? Explain.

8. Electricity flows into a hairdryer when it is plugged into a socket. If electricity has been added to the hairdryer, why doesn’t it keep operating for a while after being unplugged?

1.31.3 – E– ELECTRICALLECTRICAL S SAFETYAFETY

Electricity is always trying to get to the _______________. Like all good travelers, electricity takes the _________________ and

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_______________ route whenever it can. If something that ______________ electricity gives electricity an ___________ path to the ground, electricity will take it!

______________ and _____________ are some of the best conductors for electricity. Because your body is mostly water, you are a great _________________. So if you touch a _________________ and the _______________ at the same time, you will become electricity’s easiest path. Electricity will flow through you, and you could be seriously hurt or even killed.

You don’t have to be touching the ground directly to conduct electricity. You could also be touching something that is in contact with the ground, like a tree or a ladder.

Water is an ____________________ conductor. You can become electricity’s path to the ground if you are touching water that touches _____________________. Electricity would travel through the water and through you to the ground.

Amps vs. Volts

Which one is more dangerous?

The number of _____________ is much more important than _______________ when assessing the potential _____________ of an electrical shock

If 0.001 A passes through your body you probably wouldn’t feel it 0.015 A – 0.020 A will cause you to lose muscle control and a painful shock Current as low as 0.1 A can be fatal

Check and Reflect – Pg. 287

1. What is more dangerous, current or voltage? Why?

2. What is the purpose of a fuse?

3. What is meant by a “ground wire”?

4. What is a short circuit?

5. A power line carrying a high current falls on a car, but the people inside are not electrocuted. Explain.

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6. Are all electric shocks to the body dangerous? Explain.

7. Tall buildings often have a steel lightning rod that is connected to the ground with a wire. Lightning tends to strike these rods during storms. Why are these rods added and how do they work?

8. A friend has told you about plugging in a radio and putting on the edge of the tub while taking a bath. Why is it unwise to listen to music this way?

9. Why is it a bad idea to take shelter under a tree in a thunderstorm?

10. You notice a friend removing the third prong of a plug so that the plug will fit into an extension cord that has only two holes. Is the removal of this prong safe? Explain why or why not.

1.4 – C1.4 – CELLSELLS ANDAND B BATTERIESATTERIES

Luigi Galvani (1737-1798), who noticed that a frog’s muscle would twitch when touched by two different metals, could hardly have imagined the outcome of his observations. Galvani believed that the frog’s tissue had a unique ability to generate “animal electricity”.

Later, Alessandro Volta showed that a ______________ could be generated without using living tissue by placing ___________________ metals in a solution containing a _________________ or ________________. Today, such a device is called an ____________________ cell.

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In any electrochemical _____________, two different metal conductors are surrounded by an ____________________, a substance that can conduct electricity because it contains chemicals that form _______________.

Dry Cells

A _________ cell is a cell which contains chemicals in the form of a _________________.

The chemicals undergo a chemical ___________________ to release free __________________ from the negative terminal which pass through the device using the cell as a power source before returning to the positive terminal of the cell.

They have the advantage of not __________________ (can be used in any position) because they are sealed.

An ____________________ is found in the cell which conducts electricity because it can form ions. The electrolyte paste reacts with the two _____________, called ______________________. As a result of this reaction, one end becomes positively charged while the other end becomes negatively charged.

Wet Cells

Wet cells use a ___________________ electrolyte. The reaction remains the same:

___________________ are released from one ________________ and travel through a ____________ to another ___________________, creating an electric current.

Car batteries contain several wet cells.

Cells vs. Batteries

The chemical __________________ in a cell determines the potential difference (_____________) that the cell can create. Very few single cells can produce more than 2 V. To obtain higher voltages, __________________________ contain several ______________ connected in a __________.

Rechargeable Cells

If a cell _________________ be recharged (a ___________________ cell), the _________________ of chemicals it contains determines the total amount of electric ________________ the cell can produce.

Rechargeable __________________ cells use chemical reactions that can be __________________.

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In a re-charger, ____________________ is forced through the “dead” cell, rebuilding the original ____________________ allowing the cell to be _______________.

Electrochemistry and Electroplating

Electrochemistry – The study of chemical reactions involving _____________________.

Electrolysis – The ______________ of using __________________ to _______ molecules into their elements. The ________________ of water splits the molecules into pure hydrogen and pure oxygen.

Electroplating – The deposition of a metallic ____________ onto an ___________ by putting a negative charge onto the object and immersing it into a solution which contains a salt of the metal to be deposited.

The metallic ions of the salt carry a positive charge and are attracted to the negative part. When they reach it, the _________________ charged part provides the ________________ to reduce the positively charged ions to metallic form. ___________________ is used to coat cheaper metal with silver or gold to create jewelry and other products which look good, but are less ________________ than pure gold or silver.

Check and Reflect – Pg. 294

1. What is electrolysis? Give one example of an application of electrolysis.

2. What is an electrolyte?

3. What was Allessandro Volta’s contribution to battery technology?

4. How does a rechargeable cell work?

5. Which would be a more practical source of electricity for a car: a wet cell or a dry cell? Why?

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6. Describe the components of a wet cell and explain how the cell produces electricity. Use a diagram in your answer.

7. Dry cells are designed to keep electrons flowing. Why do they eventually “die” (stop working)?

8. Draw a diagram of an electroplating apparatus that would coat copper with gold. Be sure to label all parts of your apparatus.

10. A car designer has proposed a new car battery. She is planning to test the following different electrode combinations:

a. Both zincb. Zinc and copperc. Both copperd. Zinc and carbone. Both carbon

Will all of these combinations work? Explain why or why not.

Section Review – Pg. 295

1. Describe the charged particles in an atom.

2. What are electrodes? Explain their role in a dry cell.

3. What is the difference between a cell and a battery?

4. State three guidelines for electrical safety.

5. Describe how a static charge might build up on you as you walk across a carpet.

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6. Some cells are rechargeable. Others must be discarded when they run out of energy. Explain the difference between these two cell types.

7. Fuses are designed to interrupt the flow of current. Why are they included in a circuit?

8. Lightning is a dangerous discharge of electrons built up by friction between air and water molecules in a cloud. Is this discharge current electricity or static electricity? Explain the reason for your choice.

9. Static discharges are classified as electricity, but cannot provide the energy to operate your household devices. Why?

10. Computer circuits can be damaged by static discharges. To prevent this, technicians usually wear an anti-static strap that is connected to the metal case of the computer. Explain how wearing such a strap protects computer circuits.

11. A tall tree stands in a yard, towering over a one-storey house. There are no other trees in the area. A car is parked on the street. Which object is most likely to be struck by lightning: the tree, the house or the car? Explain your answer.

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