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Esthetician (NIC Theory Exam) · Scientific Concepts

Esthetician (NIC Theory Exam): Hair, Electricity, and Safety Concepts

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Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.

Overview

This chapter covers the basics of hair, electricity, and workplace safety. These topics are linked because estheticians use electrical devices and chemicals near clients. The exam asks simple definitions and safe habits.

A strand of hair has three layers. The cuticle is the outer layer of overlapping scales, the cortex is the middle layer that gives strength and color, and the medulla is the center, which is not always present. The hair grows from a follicle, and the growth cycle has three phases. Anagen is growth, catagen is a short transition, and telogen is rest.

Electricity is measured with a few basic units. The volt measures the pressure pushing the current, the ampere measures the amount of current, and the ohm measures resistance. A conductor lets current flow easily, and an insulator blocks it. Direct current flows one way, while alternating current switches direction.

Safe equipment use means keeping cords and plugs in good shape, keeping cords, plugs, and outlets dry, and not overloading outlets. A fuse or circuit breaker stops the current if there is too much. A Safety Data Sheet explains the hazards of each chemical, and chemicals should be kept in labeled, closed containers.

Key concepts

  • Hair layers

    The cuticle is the outer protective layer, the cortex is the middle layer with strength and pigment, and the medulla is the center core.

    Memory tipCuticle outside, cortex middle, medulla middle-most.

  • Anagen

    The active growth phase of the hair cycle, when the hair bulb makes new hair. Most scalp hairs are in this phase at any time.

    Memory tipAnagen = active.

  • Catagen

    A short transition phase when growth stops and the follicle shrinks.

    Memory tipCatagen = changing.

  • Telogen

    The resting phase before the hair sheds and a new hair begins.

    Memory tipTelogen = tired, resting.

  • Volt, ampere, ohm

    A volt measures electrical pressure, an ampere measures the strength of current, and an ohm measures resistance to flow.

    Memory tipVolt = push, amp = amount, ohm = obstacle.

  • Conductor and insulator

    A conductor, such as metal or water, lets electricity pass. An insulator, such as rubber or plastic, blocks it.

    Memory tipRubber protects; water carries.

  • Safety Data Sheet (SDS)

    A document from the maker that lists a chemical's hazards, first aid, and safe handling. A salon should keep one for each hazardous chemical product it uses.

    Memory tipQuestion about a chemical? Look at the SDS.

    Source: OSHA Hazard Communication Standard · as of 2012

Often tested

  • Hair growth order is anagen, catagen, telogen.
  • Never touch devices or plugs with wet hands, and keep cords, plugs, and outlets dry.
  • A circuit breaker or fuse stops too much current.
  • Keep chemicals in labeled containers and never mix them.
  • Use the SDS for hazards and first aid.

Easy to confuse: Electrical units

UnitMeasuresThink of
VoltPressure of the currentWater pressure
AmpereAmount of currentAmount of water flowing
OhmResistanceA narrow pipe

3 sample questions

Verified practice questions from this unit.

Practice questionReviewedScientific Concepts › Hair, Electricity, and Safety★★★★☆

Question 1. What protein is hair mostly made of?

  1. ① Melanin
  2. ② Elastin
  3. ③ Sebum
  4. ④ Keratin
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ④ Keratin

Key point: Hair is made of keratin

Hair, skin, and nails are made mostly of the tough protein keratin.

Wrong choices

  • Melanin: Melanin is pigment inside hair.
  • Elastin: Elastin is stretchy fibre in the dermis.
  • Sebum: Sebum is oil.
Practice questionReviewedScientific Concepts › Hair, Electricity, and Safety★★★★☆

Question 2. Which phase of the hair growth cycle is the active growing phase?

  1. ① Anagen
  2. ② Catagen
  3. ③ Telogen
  4. ④ Papilla
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ① Anagen

Key point: Anagen = growth

In anagen the cells of the bulb divide and the hair grows longer.

Wrong choices

  • Catagen: Catagen is the short transition phase.
  • Telogen: Telogen is the resting phase.
  • Papilla: The papilla is a structure, not a phase.
Practice questionReviewedScientific Concepts › Hair, Electricity, and Safety★★★★☆

Question 3. What does a volt measure?

  1. ① The strength of the current
  2. ② Electrical pressure
  3. ③ Resistance
  4. ④ The power used
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ② Electrical pressure

Key point: Volt = electrical pressure

The volt measures the force that pushes current through a wire.

Wrong choices

  • The strength of the current: Current strength is measured in amperes.
  • Resistance: Resistance is measured in ohms.
  • The power used: Power is measured in watts.
Practice 5 questions from this unit →