1. Chapter 13
Basics of Electricity

2. Learning Objectives
Identify the nature of electricity and the two types of electric current.
List electrical measurements.
Understand the principles of electrical equipment safety.
Examine the main electric modalities used in cosmetology.
(continues) 2

3. Learning Objectives (continued)
Outline other types of electrical equipment that cosmetologists use and describe how to use them.
Explain electromagnetic spectrum, visible spectrum of light, and invisible light.
Compare the types of light therapy and their benefits.
WHY STUDY BASICS OF ELECTRICITY?
Cosmetologists use and rely upon a variety of electrical appliances. Knowing what electricity is and how it works will allow you to use it wisely and safely.
A basic understanding of electricity will enable you to properly use and care for your equipment and tools.
Electricity and its use impact other aspects of the salon environment, such as lighting and the temperature of styling irons. Therefore, it impacts the services you offer your clients. 3

4. Introduction
How many of these services could you offer without using electricity?
As you study this chapter, you will learn how important it is for cosmetology professionals to have a basic working knowledge of electricity
INTRODUCTION
You decided to enter this field because you love cosmetology and all the services it offers to clients: hairstyling, haircoloring, perms, facials, mani-pedis.
• How many of these services could you offer without using electricity?
• As you study this chapter, you will learn how important it is for cosmetology professionals to have a basic working knowledge of electricity 4

5. 5 LESSON ACTIVITY 1 Divide students into small groups.
Ask them to discuss and record everything they did between waking up this morning and arriving for school, beginning with the alarm clock going off.
After they have completed their list, have them indicate which tasks or events used electricity.
For example: the alarm went off–electricity (unless it was a battery powered alarm clock); took shower–electricity (if their hot water heater is electric).
After they have completed their group assignment, conduct a discussion about how during their first two hours or so of being awake today nearly every aspect of their lives was affected by electricity. 5

6. Understand Electricity
The movement of electrons from one atom to another along a conductor.
When in motion, exhibits magnetic, chemical, or thermal effects.
UNDERSTAND ELECTRICITY
Electricity is the movement of electrons from one atom to another along a conductor.
Electricity is a form of energy that, when in motion, exhibits magnetic, chemical, or thermal effects.
(continues)

7. Understand Electricity (continued)
Electric current – flow of electricity along a conductor
Conductor – material that conducts electricity
Metal
Nonconductor – does not conduct electricity
Rubber, silk, wood, glass, cement
UNDERSTAND ELECTRICITY (continued)
Electric Current
This is the flow of electricity along a conductor.
All substances can be classified as either conductors or insulators, depending on the ease with which a current can be transmitted through them.
Conductor
Any material that conducts electricity.
Most metals are good conductors.
This means that electricity will pass through the material easily.
Copper is a particularly good conductor and is used in electric wiring and electric motors.
Nonconductor
Also known as an insulator.
It is a substance that does not easily transmit electricity.
Rubber, silk, wood, glass, and cement are good insulators. 7

8. Types of Electric Current
Direct current (DC) – constant, even-flowing current going in one direction
Inverter – apparatus that changes direct current to alternating current.
Alternating current (AC) – rapid, interrupted current changing directions
Rectifier – apparatus that changes alternating current into direct current
TYPES OF ELECTRIC CURRENT 
Direct current abbreviated DC, is a constant, even-flowing current that travels in one direction only and is produced by chemical means. Flashlights, mobile telephones, and cordless hairstyling tools use the direct current produced by batteries.
An inverter is a apparatus that changes direct current to alternating current. Inverters usually have a plug and a cord. They allow you to use appliances outside of the salon or your home that normally would have to be plugged into an electric wall outlet. The mobile phone charger in a car is an example of an inverter.
Alternating current, abbreviated AC, is a rapid and interrupted current, flowing first in one direction and then in the opposite direction; it is produced by mechanical means and changes directions 60 times per second. Corded hair dryers, curling irons, electric files, and table lamps that plug into a wall outlet use alternating current.
A rectifier is an apparatus that changes alternating current (AC) to direct current (DC). Cordless electric clippers and mobile phone chargers use a rectifier to change the AC from an electric wall outlet to the DC needed to recharge their batteries.
(continues) 8

9. Types of Electric Current (continued)

10. Electrical Measurements
Volt – measures pressure
Ampere – measures strength
Milliampere – 1/1,000th of an ampere
Ohm – measures resistance
Watt – measures energy used in 1 second
Kilowatt – equals 1,000 watts
ELECTRICAL MEASUREMENTS
A volt abbreviated V and also known as voltage; the unit that measures the pressure or force that pushes electric current forward through a conductor.
An ampere abbreviated A and also known as amp (AMP); the unit that measures the strength of an electric current.
A milliampere abbreviated mA, 1/1000th of an ampere; these are used for facials and scalp treatments because amps would be too strong.
Ohm, abbreviated O; a unit that measures the resistance of an electric current. Current will not flow through a conductor unless the force (volts) is stronger than the resistance (ohms).
Watt, abbreviated W; a unit that measures how much electric energy is being used in one second. A 40-watt light bulb uses 40 watts of energy per second.
Kilowatt, abbreviated K, is 1,000 watts. The electricity in your house is measured in kilowatts per hour (kwh). A 1,000-watt (1-kilowatt) hair dryer uses 1,000 watts of energy per second.
(continues) 10

11. Electrical Measurements (continued)11

12. Practice Electrical Equipment Safety
All electrical equipment should be inspected regularly to determine whether it is in safe working order.
Careless electrical connections and overloaded circuits can result in an electrical shock, a burn, or even a serious fire.
PRACTICE ELECTRICAL EQUIPMENT SAFETY
All electrical equipment should be inspected regularly to determine whether it is in safe working order.
Careless electrical connections and overloaded circuits can result in an electrical shock, a burn, or even a serious fire. 12

13. Safety Devices Fuse Circuit breaker (continues) 13 SAFETY DEVICES
A fuse prevents excessive current from passing through a circuit. It is designed to blow out or melt when the wire becomes too hot from overloading the circuit with too much current, such as when too many appliances or faulty equipment are connected to an electricity source.
A circuit breaker is a switch that automatically interrupts or shuts off an electric circuit at the first indication of an overload. Circuit breakers have replaced fuses in modern electric circuits.
(continues) 13

14. LESSON ACTIVITY 2
Take students to the circuit breaker in the school.
If all breakers are not marked, have students make a project of determining which switches relate to which areas of the facility and label them properly.
Demonstrate how a breaker can be thrown and reset. 14

15. Safety Devices (continued)
Grounding – completes an electric circuit and carries the current safely away
Ground fault interrupters – designed to protect from electrical shock by interrupting a household circuit when there is a leak in the circuit
SAFETY DEVICES (continued)
Grounding completes an electric circuit and carries the current safely away.
All electrical appliances must have at least two rectangular electrical connections, or prongs, on the plug.
The two prongs supply electric current to the circuit.
Some appliances (especially the ones with metal casing) have a third circular electric connection that is a grounding pin.
This is called a three-prong plug.
The grounding pin is designed to guarantee a safe path of electricity and prevent the user from electric shock even if a wire comes loose.
Ground fault interrupters, commonly known as GITs, are designed to protect from electrical shock by interrupting a household circuit when there is a leak in the circuit.
GFIs are required by the electrical code for receptacles in bathrooms, kitchens, and some outside receptacles.
GFI is designed to detect currents of few milliamperes and trip a breaker at the receptacle or at the breaker panel to remove shock hazard. 15

16. Guidelines for Safe Use of Electrical Equipment
All the electrical appliances you use should be UL certified.
Read all instructions carefully before using any piece of electrical equipment.
Disconnect all appliances when not in use; pull on the plug, not the cord, to disconnect.
Inspect all electrical equipment regularly.
GUIDELINES FOR SAFE USE OF ELECTRICAL EQUIPMENT
All the electrical appliances you use should be UL certified.
Read all instructions carefully before using any piece of electrical equipment.
Disconnect all appliances when not in use; pull on the plug, not the cord, to disconnect.
Inspect all electrical equipment regularly.
(continues) 16

17. Guidelines for Safe Use of Electrical Equipment
(continued)
Keep all wires, plugs, and electrical equipment in good repair.
Use only one plug in each outlet.
Avoid contact with water and metal surfaces when using electricity.
Keep electrical cords off the floor and away from everyone’s feet.
GUIDELINES FOR SAFE USE OF ELECTRICAL EQUIPMENT (continued)
Keep all wires, plugs, and electrical equipment in good repair.
Use only one plug in each outlet; overloading may cause the circuit breaker to pop.
If more than one plug is needed in an area, use a power strip with a surge protector.
Avoid contact, for both you and your client, with water and metal surfaces when using electricity, and do not handle electrical equipment with wet hands.
Keep electrical cords off the floor and away from everyone’s feet; getting tangled in a cord could cause you or your client to trip.
(continues) 17

18. Guidelines for Safe Use of Electrical Equipment
(continued)
Do not leave your client unattended while the client is connected to an electrical device.
Do not attempt to clean around electric outlets while equipment is plugged in.
Do not touch two metal objects at the same time if either is connected to an electric current.
GUIDELINES FOR SAFE USE OF ELECTRICAL EQUIPMENT (continued)
Do not leave your client unattended while the client is connected to an electrical device.
Do not attempt to clean around electric outlets while equipment is plugged in.
Do not touch two metal objects at the same time if either is connected to an electric current.
(continues) 18

19. Guidelines for Safe Use of Electrical Equipment (continued)
Do not step on or place objects on electrical cords.
Do not allow electrical cords to become twisted; this can cause a short circuit.
Do not attempt to repair electrical appliances on your own.
GUIDELINES FOR SAFE USE OF ELECTRICAL EQUIPMENT (continued)
Do not step on or place objects on electrical cords.
Do not allow electrical cords to become twisted; this can cause a short circuit.
Do not attempt to repair electrical appliances on your own. 19

20. LESSON ACTIVITY 3
Have students inspect their kit items such as curling irons, blow dryers, and other equipment in the classroom for UL approval. 20

21. One Plug Per Outlet 21 ONE PLUG PER OUTLET Instructor Demonstration
Show the different types of plugs to students. 21

22. Understand Electrotherapy
Electrotherapy – the use of electrical currents to treat the skin
Electrode (probe) – an apparatus that conducts the electric current from the machine to the client’s skin
Polarity – positive or negative state of electric current; electrotherapy devices have a negatively charged pole and a positively charged pole
UNDERSTAND ELECTROTHERAPY
The use of electrical currents to treat the skin is commonly referred to as electrotherapy. The currents used in electrical facial and scalp treatments are called modalities.
An electrode also known as a probe, this is an apparatus that conducts the electric current from the machine to the client’s skin. It is usually made of carbon, glass, or metal. Each modality requires two electrodes (one negative and one positive), except for the Tesla -high-frequency.
The polarity is the positive or negative state of electric current; electrotherapy devices have a negatively charged pole and a positively charged pole. 22

23. Polarity
Positive pole (anode, red): marked with a P and a plus (+) sign
Negative pole (cathode, black): marked with an N or a minus (–) sign
POLARITY
The positive or negative state of an electric current.
Electrotherapy equipment has a negatively charged pole and a positively charged pole.
An anode is the positive pole, red, and is marked with a “p” or plus (+) sign
A cathode is the negative pole, black, and is marked with an “n” or minus (–) sign 23

24. Modalities Galvanic current Microcurrent Tesla high-frequency current
The main modalities used in cosmetology are
Galvanic current
Microcurrent
Tesla high-frequency current
(continues) 24

25. Galvanic Current
Constant, direct current having a positive and negative pole and producing chemical changes when it passes through the tissues and fluids of the body.
Produces two actions:
Active electrode – used on area to be treated
Inactive electrode – opposite from active electrode
GALVANIC CURRENT
Galvanic current Is a constant and direct current, having a positive and negative pole that produces chemical changes when it passes through the tissues and fluids of the body.
The active electrode is the electrode used on the area to be treated.
The inactive electrode is the opposite pole from the active electrode.
The effects produced by the positive pole are the exact opposite of those produced by the negative pole.
Galvanic current is used to infuse water soluble products into unbroken skin and the scientific term for that process is called phoresis. 25

26. Galvanic Current (continued)
Iontophoresis – process of introducing water- soluble products in the skin with the use of electric current
Cataphoresis – forces acidic substances into deeper tissues from positive toward negative pole
Anaphoresis – forces liquids into tissues from negative toward positive pole
Desincrustation – used to soften and emulsify great deposits in hair follicles and pores
GALVANIC CURRENT
Iontophoresis is the process of introducing water-soluble products in the skin with the use of electric current, such as the use of the positive and negative poles of a galvanic machine.
Cataphoresis infuses an acidic (positive) product into deeper tissues using galvanic current from the positive pole toward the negative pole.
Anaphoresis infuses an alkaline (negative) product into the tissues from the negative pole toward the positive pole.
Desincrustation is a form of anaphoresis and is a process used to soften and emulsify grease deposits (oil) and blackheads in the hair follicles. 26

27. Microcurrent
An extremely low level of electricity that mirrors the body’s natural electrical impulses
Can be used for iontophoresis, firming, toning, and soothing skin
MICROCURRENT
Microcurrent is an extremely low level of electricity that mirrors the body’s natural electrical impulses.
It can be used for iontophoresis, firming, toning, and soothing skin.
It also can help heal inflamed tissue, such as acne.

28. Microcurrent Benefits
Improves blood and lymph circulation
Produces acidic and alkaline reactions
Opens and closes hair follicles and pores
Increases muscle tone
MICROCURRENT BENEFITS
Microcurrent can be effective in the following ways:
Improves blood and lymph circulation
Produces acidic and alkaline reactions
Opens and closes hair follicles and pores
Increases muscle tone
(continues)

29. Microcurrent Benefits (continued)
Restores elasticity
Reduces redness and inflammation
Minimizes healing time for acne lesions
Improves the natural protective barrier of the skin
Increases metabolism
MICROCURRENT BENEFITS (continued)
Restores elasticity
Reduces redness and inflammation
Minimizes healing time for acne lesions
Improves the natural protective barrier of the skin
Increases metabolism

30. Tesla High-Frequency Current
Characterized by high rate of oscillation or vibration
Used for scalp and facial treatments
Used to treat thinning hair, itchy scalp, and excessively oily or dry skin and scalp
Primarily heat producing
Stimulating or soothing, depending on the method
Usually made from glass or metal
TESLA HIGH-FREQUENCY CURRENT
Also known as violet ray, is a thermal or heat-producing current with a high rate of oscillation or vibration that is commonly used for scalp and facial treatments.
Tesla current does not produce muscle contractions, and the effects can be either stimulating or soothing, depending on the method of application.
The electrodes are made from either glass or metal and only one electrode is used to perform a service .

31. Tesla Current Benefits
Stimulates blood circulation
Increases elimination and absorption
Increases skin metabolism
Improves germicidal action
Relieves skin congestion
TESLA CURRENT BENEFITS
CAUTION: Never use Tesla high-frequency current on clients who are pregnant, epileptic, or asthmatic; or who have high blood pressure, excessive fillings in the teeth, sinus blockage, a pacemaker, or metal implants.
The benefits of the Tesla high-frequency current are:
Stimulates blood circulation
Increases elimination and absorption
Increases skin metabolism
Improves germicidal action
Relieves skin congestion
Instructor Demonstration
Display and demonstrate each piece of electrical implement. Pass them around the room; let students handle them. 31

32. Identify Other Electrical Equipment
Hood dryers and heat lamps
Ionic hair dryers and irons
Curling and flat irons
Heating caps
Processing and accelerating machines
Steamers and vaporizers
Light-therapy equipment
IDENTIFY OTHER ELECTRICAL EQUIPMENT
Hood dryers, heat lamps: Sources of dry heat that can be used to shorten chemical processing time.
Ionic hair dryers and irons: Effective at combating static electricity and flyaway hair.
Curling or flat irons: Have built-in heating elements and plug directly into a wall outlet. Thermal styling tools now have the capacity to get extremely hot.
Heating caps: Provide a uniform source of heat and can be used with hair and scalp conditioning treatments.
Haircolor processing or accelerating: Shorten the time it takes to process chemical hair services. These processors usually look similar to a hood dryer and dispense a hot water vapor inside the hood.
Steamer or vaporizers: Produce moist, uniform heat that can be applied to the head or face.
Light therapy equipment: Includes lasers, light-emitting diode (LED), and intense pulse light. These types of equipment are medical devices and should be used only by licensed professionals. 32

33. Explain Light Energy and Light Therapy
Electromagnetic spectrum – the name given to all forms of energy
Wavelength – the distance between successive peaks of electromagnetic waves
Long wavelengths: have a low frequency
Short wavelengths: have a higher frequency
EXPLAIN LIGHT ENERGY AND LIGHT THERAPY
Electromagnetic spectrum, also known as electromagnetic spectrum of radiation, is the name given to all of the forms of energy (or radiation) that exist.
Wavelength is the distance between successive peaks of electromagnetic waves
– Long wavelengths: Have a low frequency
– Short wavelengths: Have a higher frequency

34. Waveform
Waveform
The measurement of the distance between two wavelength
WAVEFORM
The measurement of the distance between two wavelengths

35. Visible Spectrum of Light
Visible spectrum of light – the part of the electromagnetic spectrum that can be seen
Visible light makes up only 35 percent of natural sunlight.
Violet has shortest wavelength.
Red has longest wavelength.
Infrared is just below red; ultraviolet is just above violet
VISIBLE SPECTRUM OF LIGHT
The part of the electromagnetic spectrum that can be seen.
Visible light makes up only 35 percent of natural sunlight.
Within the visible spectrum of light, violet has the shortest wavelength and red has the longest.
The wavelength of infrared light is just below that of red light and the wavelength of ultraviolet light is just above that of violet light.
(continues) 35

36. Visible Spectrum of Light (continued)

37. Invisible Light
The light at either end of the visible spectrum of light that is invisible to the naked eye
Before the visible violet light of the spectrum is ultraviolet, the shortest and least penetrating light of the spectrum.
Beyond visible red light is infrared, which produces heat.
INVISIBLE LIGHT
The light at either end of the visible spectrum of light that is invisible to the naked eye.
Before the visible violet light of the spectrum is ultraviolet light; it is the shortest and least penetrating light of the spectrum.
Beyond the visible red light of the spectrum is infrared light, which produces heat.

38. Ultraviolet (UV) Light
Invisible
Has short wavelength for higher energy
Less penetrating than visible light
Accelerates chemical reactions
Produces less heat than visible light
Kills some germs
ULTRAVIOLET (UV) LIGHT
Abbreviated UV light
Also known as cold light or actinic light
Invisible light that has a short wavelength (giving it higher energy)
Less penetrating than visible light
Causes chemical reactions to happen more quickly than visible light
Produces less heat than visible light, and kills some germs

39. Types of UV Light
UVA – has the longest wavelength of the UV light spectrum and penetrates dermis; damages collagen and elastin
UVB – often called the burning light; frequently associated with sunburns
UVC – blocked by the ozone layer
TYPES OF UV LIGHT
There are three types of UV light.
Ultraviolet A light has the longest wavelength of the UV light spectrum and penetrates directly into the dermis of the skin, damaging the collagen and elastin. UVA light is the light that is often used in tanning beds.
Ultraviolet B light is often called the burning light because it is most associated with sunburns. Excessive use of both UVA and UVB light can cause skin cancers.
Ultraviolet C light is blocked by the ozone layer. If the Earth loses the protective layer of the ozone, life will no longer exist as we know it. We do not want to deplete the ozone layer because it protects us from UVC radiation.

40. Infrared Light Infrared Light
Used mainly for hair conditioning treatments and to process color
Has longer wavelengths
Penetrates deeply
Makes up 60 percent of natural sunlight
Used to warm muscles
Can diminish signs of aging
INFRARED LIGHT
Has longer wavelengths, penetrates more deeply, has less energy, and produces more heat than visible light. Infrared light makes up 60 percent of natural sunlight.
Infrared lamps are used mainly during hair conditioning treatments and to process haircolor.
They are also used in spas and saunas for relaxation and for warming up muscles.
Infrared light has been used to diminish signs of aging such as wrinkles, to heal wounds, and to increase circulation.

41. Light Versus Heat and Energy
Catalysts – used to speed up chemical reactions; some use heat and absorb energy like a battery; they pass energy to an initiator and reaction begins
Light therapy – also known as phototherapy; the application of light rays to skin for hair removal or treatment of wrinkles, capillaries, or pigmentation
LIGHT VERSUS HEAT AND ENERGY 
Catalysts are substances that speed up chemical reactions. Some catalysts use heat as an energy source while others use light. Whatever the energy source, catalysts absorb energy like a battery.
Light therapy, also known as phototherapy, is the application of light rays to the skin for the treatment of wrinkles, capillaries, pigmentation, or hair removal.

42. Lasers
Acronym for Light Amplification by Stimulated Emission of Radiation
Photothermolysis – turns light from laser into heat
Can remove blood vessels and tattoos
Can disable hair follicles
Can eliminate some wrinkles
LASERS
Acronym for Light Amplification Stimulation Emission of Radiation; it uses electromagnetic radiation for hair removal and skin treatments.
Photothermolysis is a process that turns the light from the laser into heat.
Can remove blood vessels
Can disable hair follicles
Can remove tattoos
Can eliminate some wrinkles
© carol.anne/ Shutterstock.com

43. How Lasers Work
By means of a medium (solid, liquid, gas or semiconductor).
Medium emits light when stimulated by power.
Reflective surfaces in chamber create light.
Light passes back and forth and gains energy.
HOW LASERS WORK
Lasers work by means of a medium (solid, liquid or gas, or semiconductor) that emits light when stimulated by a power source.
The medium is placed in a specifically designed chamber with mirrors located inside both ends.
That chamber is stimulated by an energy source, such as electric current, which, in turn, stimulates the particles.
The mirrors create light that becomes trapped and goes back and forth through the medium, gaining energy with each pass.
The medium determines the wavelength of the laser and its use.
Most lasers are classified as Level II or above, which means that the practitioner should be working under the supervision of a qualified physician. 43

44. Laser Hair Removal

45. Light-Emitting Diode (LED)
A medical device used to reduce acne, increase blood circulation, and improve collagen content in the skin
Courtesy of Revitalight.
LIGHT-EMITTING DIODE (LED)
Abbreviated LED, is a medical device used to reduce acne, increase blood circulation, and improve the collagen content in the skin.

46. LED Effects Releases light onto skin
Stimulates specific responses at precise depths of skin tissues
Seeks chromophore – color component within skin such as blood or melanin
Tissue depth triggers reaction such as stimulating circulation or reducing bacteria.
LED EFFECTS
Releases light onto skin.
Stimulates specific responses at precise depths of skin tissue.
Seeks chromophore – a color component within the skin such as blood or melanin.
Tissue depth triggers a reaction such as stimulating circulation or reducing bacteria.

47. Beneficial Effects of LED Therapy
LED EFFECTS (continued)
Blue light LED reduces acne and bacteria.
Red light LED increases circulation and improves collagen and elastin production.
Yellow light LED reduces swelling and inflammation.
Green light LED reduces hyperpigmentation.
Blue light LED is used for precancerous lesions.

48. Intense Pulse Light
Device that uses multiple colors and wavelengths (broad spectrum) of focused light to treat spider veins, hyperpigmentation, rosacea and redness, wrinkles, enlarged hair follicles and pores, and excessive hair.
Treatments are provided under the supervision of a physician.
INTENSE PULSE LIGHT
A medical device that uses multiple colors and wavelengths (broad spectrum) of focused light to treat spider veins, hyperpigmentation, rosacea and redness, wrinkles, enlarged hair follicles and pores, and excessive hair.
As with most devices, multiple treatments are required.
These treatments are provided only under the supervision of a qualified physician.

49. Summary and Review
Because many of the devices and pieces of equipment we use in beauty services are electrical it is important to have a general understanding of the basics of electricity.
We cannot perform various skin care services safely and effectively without understanding which form of electrical current will give the best results for the desired service.
SUMMARY AND REVIEW
• Because many of the devices and pieces of equipment we use in beauty services are electrical, it is important to have a general understanding of the basics of electricity.
• We cannot perform various skin care services safely and effectively without understanding which form of electrical current will give the best results for the desired service. 49

50. Chapter Review Questions
Define electric current.
Explain the difference between a conductor and a nonconductor (insulator).
Describe the two types of electric current and give examples of each.
Explain the difference between a volt and an amp.
CHAPTER REVIEW QUESTIONS
1. Define electric current.
Answer: Electric current is the flow of electricity along a conductor.
2. Explain the difference between a conductor and a nonconductor (insulator).
Answer: A conductor is any substance that conducts electricity, such as metal, copper, or ordinary water. A nonconductor, or insulator, is a material that does not transmit electricity easily, such as rubber, silk, wood, glass, and cement.
3. Describe the two types of electric current and give examples of each.
Answer: The two types of current are as follows:
Direct current (DC) is a constant, even-flowing current that travels in one direction only. Examples are flashlights, mobile telephones, and cordless hairstyling tools. All use batteries.
Alternating current (AC) is a rapid and interrupted current, flowing first in one direction and then in the opposite direction. Examples are corded hair dryers, curling irons, electric files, and table lamps. All plug into a wall outlet and use alternating current.
4. Explain the difference between a volt and an amp.
Answer: The difference between a volt and an amp is that a volt is the unit that measures the pressure or force that pushes electricity through a conductor. An amp is the unit that measures the strength of an electric current.
(continues) 50

51. Chapter Review Questions (continued)
Define ohm.
Define watt and kilowatt.
Explain the function of a fuse.
What is the purpose of a circuit breaker?
What is the purpose of grounding?
CHAPTER REVIEW QUESTIONS (continued)
5. Define ohm.
Answer: An ohm is a unit that measures the resistance of an electric current. Current will not flow through a conductor unless the force (volts) is stronger than the resistance (ohms).
6. Define watt and kilowatt.
Answer: A watt is a measurement of how much electric energy is being used in one second. A kilowatt (K) is 1,000 watts.
7. Explain the function of a fuse.
Answer: A fuse prevents excessive current from passing through a circuit. It is designed to blow out or melt when the wire becomes too hot from overloading the circuit with too much current, such as when too many appliances or faulty equipment are connected to an electricity source. 
8. What is the purpose of a circuit breaker?
Answer: A circuit breaker is a switch that automatically interrupts or shuts off an electric circuit at the first indication of an overload. Circuit breakers have replaced fuses in modern electric circuits. They have all the safety features of fuses but do not require replacement and can simply be reset.
9. What is the purpose of grounding?
Answer: The purpose of grounding is to complete an electric circuit and carry the current safely away.
(continues) 51

52. Chapter Review Questions (continued)
List at least five steps to take for electrical safety.
CHAPTER REVIEW QUESTIONS (continued)
10. List at least five steps to take for electrical safety.
Answer:
All the electrical appliances you use should be UL certified.
Read all instructions carefully before using any piece of electrical equipment.
Disconnect all appliances when not in use.
Inspect all electrical equipment regularly.
Keep all wires, plugs, and electrical equipment in good repair.
Use only one plug for each outlet; overloading may cause the circuit breaker to pop. If more than one plug is needed in an area, use a power strip with a surge protector.
Avoid contact, for both you and your client, with water and metal surfaces when using electricity, and do not handle electrical equipment with wet hands.
Do not leave your client unattended while connected to an electrical device.
Keep electrical cords off the floor and away from people’s feet; getting tangled in a cord could cause you or your client to trip.
Do not attempt to clean around electric outlets while equipment is plugged in.
Do not touch two metal objects at the same time if either is connected to an electric current.
Do not step on or place objects on electrical cords.
Do not allow electrical cords to become twisted; this can cause a short circuit.
Disconnect appliances by pulling on the plug, not the cord.
Do not attempt to repair electrical appliances unless you are qualified.
(continues) 52

53. Chapter Review Questions (continued)
List and describe the three main electric modalities (currents) used in cosmetology.
What are electromagnetic spectrum of radiation, visible light, and white light?
CHAPTER REVIEW QUESTIONS (continued)
11. List and describe the three main electric modalities (currents) used in cosmetology.
Answer: The three main electrical modalities (currents) used in cosmetology are:
Galvanic current: this is a constant and direct current. It has a positive and negative pole and produces chemical changes when it passes through the tissues and fluids of the body.
Microcurrent is an extremely low level of electricity that mirrors the body’s natural electrical impulses. Microcurrent can be used for iontophoresis, firming, toning, and soothing skin. It also can help heal inflamed tissue such as acne.
Tesla high-frequency current: this is a thermal or heat-producing current with a high rate of oscillation or vibration. It is commonly called violet ray and is used for scalp and facial treatments. It does not produce muscle contractions. The effects of this type of current can be either stimulating or soothing, depending on the method of application.
12. What are electromagnetic spectrum of radiation, visible light, and white light invisible light?
Answer: Electromagnetic spectrum: Also known as electromagnetic spectrum of radiation is the name given to all of the forms of energy (or radiation) that exist. It carries, or radiates, energy through space on waves. These waves are similar to those caused when a stone is dropped on the surface of water.
Visible light: It is the primary source of light used in facial and scalp treatments. It can be seen. Visible light makes up 35 percent of natural sunlight.
Invisible light: is the light at either end of the visible spectrum of light that that is invisible to the naked eye.
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54. Chapter Review Questions (continued)
List and describe the two main types of light therapy.
What are the benefits of LED therapies?
Identify the colors of LED lights and their wavelengths (nm)?
Name two important precautions to observe when using light therapy.
CHAPTER REVIEW QUESTIONS (continued)
13. List and describe the two main types of light therapy.
Answer: The two main types of light therapy are:
Infrared light: Makes up 60 percent of natural sunlight. It has longer wavelengths, penetrates the deepest, has less energy, and produces more heat than visible light.
Ultraviolet (UV) light: Also referred to as cold light or actinic light and makes up 5 percent of natural sunlight. UV light is the least penetrating, produces chemical effects, kill germs, and prompts skin to produce Vitamin D.
14. What are the benefits of LED therapies?
Answer: They emit light onto the skin to stimulate specific responses at precise depth of the skin tissue. They can reduce acne, improve collagen and elastin production, and reduce hyper pigmentation. 
15. Identify the colors of LED lights and their wavelengths (nm)?
Answer:
Blue light-570 nm
Red light-640 nm
Yellow light-590 nm
Green Light-525 nm.
16. Name two important precautions to observe when using light therapy.
Answer: Two important precautions to observe when using light therapy are:
Always protect the client’s eyes. The cosmetologist should wear safety goggles.
Avoid overexposure to UV rays. It can produce painful burns and blistering, increase risk of skin cancer, and cause premature aging. 54