Chapter 1-2: Introduction and Unit Measurements

Created by Marianne Krisha Oraye

It is also known as a VOM (Volt-Ohm-Milliammeter) or multitester, is an essential electronic tool designed to measure electrical parameters, specifically voltage (V), current (I), and resistance (R).

Multimeter

It is a short electrical wire with connector pins or tips at each end, designed to bridge, connect, or prototype circuits on a breadboard or other testing components.

jumper wire

It is a highly efficient semiconductor device that emits light when an electric current passes through it, commonly used for lighting, indicators, and displays.

light-emitting diode (LED)

It is an electronic circuit or device that automatically maintains a constant, stable output voltage regardless of input voltage variations or load changes.

Power Regulator

It is a reusable, plastic base with internal metal clips, used for prototyping electronic circuits without soldering.

solderless breadboard

It is a passive, two-terminal electrical component that creates resistance to the flow of electric current, measured in Ohms.

Resistor

They act as manual controllers to open (break) or close (connect) an electrical circuit, allowing or stopping current flow.

Buttons & Switches

It is a compact DC power source (often PP3 size) that provides 9 volts of potential energy by connecting six internal 1.5V cells in series.

9V Battery

Electrostatic Discharge (ESD)

It is the sudden flow of electricity between two charged objects caused by contact, an electrical short, or dielectric breakdown.

It is the electrical pressure or potential difference between two points that causes electrons to flow.

Voltage (V)

What is the SI unit of volts? It is defined as the energy consumption of one joule per coulomb of electric charge (J/C).

Volt (V)

It is the net rate of flow of electric charge—typically electrons—through a conductive medium, such as a wire. It represents the quantity of electricity moving past a specific point over time.

Current (I)

What is the SI unit of electric current? It represents the flow of electric charge at a rate of one coulomb per second (C/s).

Ampere (A)

It is a fixed, agreed-upon standard we use to compare and communicate measurements.

Unit

It is the modern metric system and the world's most widely used standard for measurement.

SI unit system (Système International d'Unités)

SI unit of length

meter (m)

SI unit of time

second (s)

SI unit of mass

gram (g)

SI unit of temperature

Kelvin (K)

SI unit of luminous intensity

Candela (cd)

SI unit of amount of substance

mole (mol)

What arithmetic operation do you use when you are converting from Larger prefix to Smaller unit?

Multiply

What arithmetic operation do you use when you are converting from Smaller prefix to Larger unit?

Divide

What is the value of Giga? (Answer format: with comma and no space)

1,000,000,000

What is the value of Mega? (Answer format: with comma and no space)

1,000,000

What is the value of Kilo? (Answer format: with comma and no space)

1,000

What is the value of milli?

0.001

What is the value of micro?

0.000001

What is the value of nano?

0.000000001

What are the significant figures?

a. Non-zero

b. Leading zeros

c. trailing zeros with a decimal

d. trailing zero in whole numbers

a, c, and d

(Topic: Safety – Nature of Current in This Book)

According to the text, why is the current used in this book inherently fairly safe?

A) Because the voltage is always below 1 volt
B) Because all circuits are sealed in plastic
C) Because small batteries are not capable of delivering the amount of current needed to injure or harm
D) Because it uses alternating current (AC) which is harmless

Correct Answer: C
Explanation: The text explicitly states: "This book deals almost entirely with direct current from small battery sources. This current is inherently fairly safe, as small batteries are not capable of delivering the amount of current needed to injure or harm."

(Topic: Safety – Main Issue with Poor Circuits)

What is the main issue that sometimes arises when working with poorly made circuits according to the text?

A) Electric shock to the user
B) Components can overheat and occasionally catch fire
C) Permanent magnetisation of tools
D) Explosion of the battery

Correct Answer: B
Explanation: The text says: "The main issue that sometimes arises is that, in poorly made circuits, components can overheat and occasionally (but rarely) catch fire."

(Topic: Safety – Battery Chemical Hazard)

Why might batteries present a chemical hazard?

A) Batteries are often made from potentially toxic chemicals
B) Batteries contain mercury only
C) Batteries produce radioactive waste
D) Batteries are filled with water

Correct Answer: A
Explanation: The text notes: "batteries are often made from potentially toxic chemicals." This is given as an additional concern beyond overheating.

(Topic: Safety – Skin Protection)

Safety guideline #1 states that if you have cuts or open areas on your skin, you should cover them. Why?

A) Because open skin can cause short circuits
B) To avoid getting chemicals from batteries into the cuts
C) To prevent infection only
D) Because your skin is where most of your electric protection exists in your body

Correct Answer: D
Explanation: The text explains: "Your skin is where most of your electric protection exists in your body." Covering cuts restores that protection.

(Topic: Safety – Before Applying Power)

What should you check before applying power to your circuit?

A) That you have not accidentally wired a short circuit between the positive and negative poles of your battery
B) That the battery is fully charged
C) That the wires are all the same color
D) That all components are brand new

Correct Answer: A
Explanation: Safety guideline #2 states: "Before applying power to your circuit, check to be sure you have not accidentally wired in a short circuit between the positive and negative poles of your battery."

(Topic: Safety – Unexpected Circuit Behavior)

If your circuit does not behave as expected when you plug in the battery, what should you do immediately?

A) Measure the voltage with a multimeter
B) Add more batteries to increase power
C) Adjust the components while powered
D) Unplug it immediately and check for problems

Correct Answer: D
Explanation: Safety guideline #3 says: "If your circuit does not behave as you expect it to when you plug in the battery, unplug it immediately and check for problems."

(Topic: Safety – Component Overheating)

What should you do if your battery or any component becomes warm?

A) Reduce the voltage by adding a resistor
B) Disconnect power immediately
C) Add a fan to cool it
D) Wait for it to cool down while still powered

Correct Answer: B
Explanation: Safety guideline #4 instructs: "If your battery or any component becomes warm, disconnect power immediately."

(Topic: Safety – Burning Smell)

What action should be taken if you smell any burning or smoky smells from your circuit?

A) Continue working but monitor closely
B) Open a window
C) Smell more to identify the component
D) Disconnect power immediately

Correct Answer: D
Explanation: Safety guideline #5 states: "If you smell any burning or smoky smells, disconnect power immediately."

(Topic: Safety – Battery Disposal)

How should batteries be disposed of according to the text?

A) By burning them
B) In regular household trash
C) In accordance with local regulations
D) By throwing them in water

Correct Answer: C
Explanation: Safety guideline #6 says: "Dispose of all batteries in accordance with local regulations."

(Topic: Safety – Rechargeable Batteries)

What should you follow for rechargeable batteries?

A) Always charge them overnight
B) The instructions on the battery for proper charging procedures
C) Never charge them
D) Only use them once

Correct Answer: B
Explanation: Safety guideline #7 states: "For rechargeable batteries, follow the instructions on the battery for proper charging procedures."

(Topic: Safety – AC and Large Batteries Danger)

Why must you exercise many more precautions when dealing with AC or large batteries (like a car battery)?

A) Because they are more expensive
B) Because they require special tools
C) Because they are heavier
D) Because they generate sufficient power to harm or kill you if mishandled (sometimes even after power is disconnected)

Correct Answer: D
Explanation: The text warns: "those devices generate sufficient power in themselves and within the circuits to harm or kill you if mishandled (sometimes even after the power has been disconnected)."

(Topic: ESD – Definition and Personal Danger)

What is electrostatic discharge (ESD), and is it dangerous to you?

A) A high-voltage arc that can kill
B) A shock you feel from a doorknob; it is not dangerous to you
C) A sound that damages hearing
D) A type of chemical reaction that is very dangerous

Correct Answer: B
Explanation: The text defines ESD with the doorknob example and states: "ESD is not dangerous to you, but it can be dangerous to your equipment."

(Topic: ESD – Damage to Equipment)

Can ESD shocks that you cannot feel damage your equipment?

A) Only if you are standing on carpet
B) Only if the equipment is powered on
C) Yes, even shocks that you can’t feel may damage your equipment
D) No, only shocks you feel are dangerous

Correct Answer: C
Explanation: The text explicitly says: "Even shocks that you can’t feel may damage your equipment."

(Topic: ESD – Environmental Risk Factor)

According to the text, when is ESD more problematic?

A) In humid environments
B) When working with batteries
C) In dry climates only
D) If you have carpet floors, as those tend to build up static electricity

Correct Answer: D
Explanation: The text states: "ESD is also more problematic if you have carpet floors, as those tend to build up static electricity."

(Topic: ESD – Storing IC Components)

How should you store IC components (electronics chips) to prevent ESD problems?

A) Wrapped in aluminum foil
B) In a metal box
C) With the leads enmeshed in conductive foam
D) In a plastic bag

Correct Answer: C
Explanation: The text advises: "When storing IC components (i.e., electronics chips), store them with the leads enmeshed in conductive foam. This will prevent any voltage differentials from building up in storage."

Topic: ESD – Clothing Recommendation)

What type of fabric does the text recommend wearing to help prevent ESD problems?

A) Synthetic polyester
B) Nylon
C) Wool
D) Natural 100% cotton fabrics

Correct Answer: D
Explanation: The text lists as a simple rule: "Wear natural 100% cotton fabrics."

(Topic: ESD – Alternative to ESD Strap/Mat)

If you don’t use an ESD strap or mat, what should you do before starting work?

A) Wear rubber gloves
B) Stand on a wooden floor
C) Wash your hands
D) Touch a large metal object before starting work, and again any time after moving around

Correct Answer: D
Explanation: The text says: "If you don’t use an ESD strap or mat, touch a large metal object before starting work. Do so again any time after moving around."

(Topic: Multimeter Precautions – Resistance Measurement)

What is the correct precaution when measuring resistance with a multimeter?

A) Measure resistance on an active circuit for accuracy
B) Leave the circuit powered but set the multimeter to voltage first
C) Take the resistor all the way out of the circuit before trying to measure it
D) Measure resistance only on high voltage settings

Correct Answer: C
Explanation: The text warns: "Do not try to measure resistance on an active circuit. Take the resistor all the way out of the circuit before trying to measure it."

(Topic: Multimeter Precautions – Choosing Settings)

What should you do before hooking up your multimeter?

A) Set it to resistance mode first regardless of measurement
B) Always use the lowest setting for current
C) Guess the value and set it to that
D) Choose the appropriate setting on your multimeter before you hook it up

Correct Answer: D
Explanation: The text instructs: "Choose the appropriate setting on your multimeter before you hook it up."

(Topic: Multimeter Precautions – High Value First)

Why should you always err on the side of choosing high values first, especially for current and voltage?

A) Because high values give more accurate readings
B) Because low values might damage the multimeter or require buying a new one
C) Because high values are easier to read
D) Because low values drain the multimeter's battery

Correct Answer: B
Explanation: The text explains: "If you set the value too large, it is easy enough to set it lower. If you had it set too low, you might have to buy a new multimeter!" This emphasizes protection of the device.

(Topic: Definition of Unit of Measurement)

What is a unit of measurement?

A) A standard against which we measure something
B) A type of scientific formula
C) A method for rounding numbers
D) Another name for the imperial system

Correct Answer: A
Explanation: The text defines: "A unit of measurement is basically a standard against which we are measuring something." Examples include feet, meters, inches, etc.

(Topic: SI Units – Full Name and Abbreviation)

What does "SI Units" stand for?

A) Standard Imperial Units
B) Scientific International Units
C) International System of Units
D) Simple Index Units

Correct Answer: C
Explanation: The text states: "The scientific community has largely agreed upon a single standard of units known as the International System of Units, abbreviated as SI Units."

(Topic: Problem with Imperial System)

According to the text, what made the imperial system confusing?

A) It had too few units
B) All units were divisible by 10
C) There were an enormous number of units, all divisible by differing amounts
D) It was based on physics

Correct Answer: C
Explanation: The text says: "The imperial system was very confusing. Not only were there an enormous number of units but they all were divisible by differing amounts." Example: 12 inches in a foot, 3 feet in a yard, 1,760 yards in a mile.

(Topic: SI Base Unit for Current)

Which of the following is an SI base unit for electric current?

A) Volt
B) Ohm
C) Ampere
D) Coulomb

Correct Answer: C
Explanation: Figure 2‑1 lists "Current" with unit "Ampere" and abbreviation "A". Volt, ohm, and coulomb are derived units.

(Topic: SI Base Unit for Mass – Clarification)

According to the text, which unit is technically the base unit of mass for historical reasons, but it makes more sense to view the gram as the base unit for prefixes?

A) Kilogram
B) Gram
C) Milligram
D) Newton

Correct Answer: A
Explanation: The footnote in Figure 2‑1 explains: "Technically, for historical reasons, the base unit of mass is actually the kilogram, but it makes more sense when thinking about it to view the gram itself as the base unit."

(Topic: SI Derived Unit – Liter)

How is a liter defined in terms of SI base units?

A) A liter is a thousandth of a cubic meter
B) A liter is one kilogram of water
C) A liter is one cubic centimeter
D) A liter is 1,000 milliliters

Correct Answer: A
Explanation: The text states: "A liter, however, is not defined on its own, but in terms of meters. A liter is a thousandth of a cubic meter."

(Topic: SI Derived Unit – Newton)

In the SI system, a newton is defined as:

A) The force of gravity on one gram
B) A kilogram‑meter per second squared
C) One meter per second squared
D) The weight of one liter of water

Correct Answer: B
Explanation: The text defines: "In the SI system, the newton is defined as being a 'kilogram‑meter per second squared.' This is another way of saying that a newton is the amount of force which accelerates 1 kilogram 1 meter per second, per second.

(Topic: Advantage of SI Prefixes)

What is the advantage of using unit prefixes in the SI system?

A) There are different unit names for every scale
B) One single set of prefixes can modify all units
C) Prefixes only work for length measurements
D) Prefixes are based on the imperial system

Correct Answer: B
Explanation: The text explains: "by memorizing one single set of prefixes, you can know how to modify all of the units in the SI system."

(Topic: Meaning of "Kilo‑" Prefix)

What does the prefix "kilo‑" mean?

A) 1,000
B) 100
C) 0.001
D) 1,000,000

Correct Answer: A
Explanation: The text states: "the prefix kilo‑ means thousand." Figure 2‑2 shows kilo = 1,000 for all units.

(Topic: Meaning of "Milli‑" Prefix)

What does the prefix "milli‑" mean?

A) 1,000
B) 0.000001
C) 0.001 (one thousandth)
D) 0.000000001

Correct Answer: C
Explanation: The text says: "The prefix milli‑ means thousandth, as in 1/1000." Figure 2‑2 confirms milli = 0.001.

(Topic: Converting Kilograms to Grams)

If something weighs 24.32 kilograms, how many grams is that?

A) 0.02432 grams
B) 2.432 grams
C) 243.2 grams
D) 24,320 grams

Correct Answer: D
Explanation: The text gives the example: "if something weighs 24.32 kilograms, then I could convert that into grams by multiplying by 1,000. 24.32 × 1000 = 24,320."

(Topic: Converting Grams to Kilograms)

If something weighs 35.2 grams, how many kilograms is that?

A) 35,200 kilograms
B) 0.0352 kilogram
C) 352 kilograms
D) 0.352 kilogram

Correct Answer: B
Explanation: The text says: "if something weighs 35.2 grams, then I could convert that into kilograms by dividing it by 1,000. 35.2/1000 = 0.0352."

(Topic: Converting Between Prefixed Units – Kilograms to Micrograms)

If something weighs 220 kilograms, how many micrograms is that? (Use: kilo = 1,000, micro = 0.000001)

A) 2,200,000 micrograms
B) 22,000,000 micrograms
C) 220,000,000,000 micrograms
D) 0.00022 micrograms

Correct Answer: C
Explanation: The text calculates: (220 × 1000) / 0.000001 = 220,000,000,000 micrograms.

(Topic: Using Prefix Chart to Convert Small Numbers)

Using Figure 2‑3, what is 0.000000030 meters expressed in nanometers?

A) 30 millimeters
B) 30 micrometers
C) 30 nanometers
D) 30 picometers

Correct Answer: C
Explanation: The text explains: "there are only zeros in the unit, the milli‑, and the micro‑ areas. The first nonzero digits appear in the 'nano‑' group. When lined up with the chart, the number in the nano‑ area is 030. Therefore, the number under consideration is 30 nanometers."

(Topic: Abbreviation for Micro‑)

Why is the Greek letter μ (mu) used as the abbreviation for the prefix "micro‑"?

A) Because micro‑ begins with m, and m is already used for milli‑ and M for mega‑
B) Because the Greek alphabet is standard in electronics
C) Because μ is easier to write than m
D) Because the SI committee decided randomly

Correct Answer: A
Explanation: The text explains: "It’s essentially the Greek way of writing the letter m, and it is used because we already have a lowercase m (milli‑) and an uppercase M (mega‑) in use."

(Topic: Alternate Writing for Micro‑)

If you see "100 us" in another book, what does it mean?

A) 100 microseconds
B) 100 milliseconds
C) 100 meters per second
D) 100 unit seconds

Correct Answer: A
Explanation: The text says: "if you are reading elsewhere something like 100 us, that means 100 microseconds." Because u is sometimes used instead of μ.

(Topic: Significant Figures – Leading Zeros)

How many significant figures does the number 0.00042 have?

A) 5
B) 4
C) 3
D) 2

Correct Answer: D
Explanation: The text states: "significant figures ignore all leading zeros. So the number 0.00042 has two significant figures."

(Topic: Significant Figures – Exact Numbers)

How are exact numbers treated in significant figure rules?

A) They are ignored
B) They have one significant figure
C) They are considered to have infinite significant digits
D) They must be rounded to three digits

Correct Answer: C
Explanation: The text says: "If a number is exact, then it is essentially considered to have infinite significant digits. For instance, it takes two people to have a baby. This is an exact number."

(Topic: Multiplication/Division Rule for Significant Figures)

For multiplication and division, how should you round the result?

A) Round to the fewest decimal places
B) Round to the input value with the most significant figures
C) Round to the same number of significant figures as the input with the fewest significant figures
D) Never round at all

Correct Answer: C
Explanation: The text explains: "For multiplying and dividing, you should find the input value with the fewest significant figures. The result should then be rounded to that many significant figures."

(Topic: Addition/Subtraction Rule for Significant Figures)

For addition and subtraction, how is the result rounded?

A) To the fewest total digits
B) To the fewest significant figures overall
C) To the most decimal places
D) To the number of decimal places of the least precise input value

Correct Answer: D
Explanation: The text says: "the result is rounded to the number of decimal places available in the input value that has the least precision (fewest numbers to the right of the decimal)."

How many nanometers is 23 meters?

23 m=23×109 nm=2.3×1010 nm (or 23,000,000,000 nm)

How many seconds is 23.7 microseconds?

23.7 μs=23.7×10−6 s=2.37×10−5 s

How many grams is 89.43 megagrams?

89.43 Mg=89.43×106 g=8.943×107 g

How many meters is 15 nanometers?

15 nm=15×10−9 m=1.5×10−8 m

How many kilograms is 0.3 microgram?

0.3 μg=0.3×10−9 kg=3×10−10 kg

How many milliseconds is 45 kiloseconds?

45 ks=45×106 ms=4.5×107 ms

What is the abbreviation for picosecond? What is the abbreviation for microgram?

• Picosecond: ps

• Microgram: μg (or ug if the Greek letter μ is unavailable)

What is the abbreviation for a terameter?

Tm

How many significant figures does the number 476 have?

3 (all non‑zero digits)

How many significant figures does the number 5 have?

1 (single non‑zero digit)

How many significant figures does the number 000352 have?

3 (leading zeros are not significant; only 352 counts)

How many significant figures does the number 0.00043 have?

2 (leading zeros ignored; digits “43” are significant)

How many significant figures does the number 1.0004 have?

5 (all digits, including zeros between non‑zeros and after decimal)

How many significant figures does the number 2.34000 have?

6 (trailing zeros after a decimal point are significant)

What is 23×523×5?

23×5=115.
23 has 2 sig figs, 5 has 1 sig fig → product must have 1 sig fig.
Answer: 100 (or 1×1021×102)

What is 23+0.623+0.6?

23+0.6=23.6.
For addition, round to the least precise decimal place. 23 has no decimal places; 0.6 has one.
Answer: 24

What is 0.005×2090.005×209?

0.005×209=1.045.
0.005 has 1 sig fig, 209 has 3 sig figs → product has 1 sig fig.
Answer: 1 (or 1×1001×100)

What is 0.0023×450.0023×45?

0.0023×45=0.1035.
0.0023 has 2 sig figs, 45 has 2 sig figs → product has 2 sig figs.
Answer: 0.10 (or 1.0×10−11.0×10−1)

What is 0.5+0.50.5+0.5?

0.5+0.5=1.0.
Both numbers have one decimal place → sum has one decimal place.
Answer: 1.0

Why are significant figures important?

Significant figures prevent us from claiming more precision than our measurements actually allow. They provide a standardized way to round results so that the precision of the input data is honestly communicated. Without them, a calculation might imply accuracy that does not exist (e.g., reporting 1/3 meter as 0.333333333 m when the original measurement was only 1 meter to one significant figure). They help scientists and engineers compare results meaningfully and avoid overconfidence in measured values.