You’ve probably seen the symbol Ω on a multimeter, resistor, circuit diagram, electronics specification, or physics worksheet and wondered, “What does the ohm symbol mean?”

The answer is surprisingly simple: Ω is the symbol for the ohm, the SI unit used to measure electrical resistance. But there’s more to the symbol than its appearance. Ω is also the uppercase Greek letter omega, and understanding the difference helps explain why this particular character is used in electrical engineering.

In this guide, we’ll explain what Ω means, how resistance works, where the symbol came from, how to calculate ohms, what the symbols Ω, kΩ, and MΩ mean, and how you’ll encounter ohms in everyday electronics.

Featured Snippet Answer:
The symbol Ω (omega) represents the ohm, the SI unit of electrical resistance. One ohm equals one volt per ampere (1 Ω = 1 V/A). It measures how strongly a component or material resists electric current. The unit is named after German physicist Georg Simon Ohm.

What Does the Ohm Symbol Ω Mean?

The symbol Ω means ohm, the SI derived unit of electrical resistance.

In simple terms, resistance describes how much a material or electrical component opposes the flow of electric current.

The relationship is:

1 Ω = 1 V/A

In other words, a resistance of one ohm exists when a potential difference of one volt produces a current of one ampere through the component under the relevant conditions. NIST identifies the ohm (Ω) as the SI unit of electrical resistance and gives the relationship 1 Ω = 1 V/A.

The official SI documentation from the Bureau International des Poids et Mesures (BIPM) also lists ohm — Ω among the SI derived units.

In plain English

Think of electricity as something moving through a system.

Resistance = opposition to current flow.

A higher resistance generally makes it harder for a given voltage to push current through a circuit.

A lower resistance generally allows more current to flow for the same voltage.

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Is Ω the Same as Omega?

The symbol is the uppercase Greek letter omega, Ω, but in electrical engineering it represents the ohm.

This distinction is important.

Ω as a Greek letter

Ω is the uppercase form of the Greek letter omega.

Ω as an electrical unit

Ω is the internationally recognized symbol for the ohm.

So if you see:

10 Ω

in an electronics context, it means:

10 ohms of resistance.

It doesn’t mean “10 omega.”

The unit’s name is ohm, while its symbol happens to be the Greek letter omega.

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Why Is the Ohm Symbol an Omega?

The ohm was named after Georg Simon Ohm, the German physicist whose work established the relationship between voltage, current, and resistance now commonly expressed through Ohm’s law.

The symbol Ω was adopted to represent the unit.

This makes Ω particularly recognizable in electrical engineering and electronics.

The BIPM’s SI documentation officially specifies Ω as the symbol for the ohm.

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What Is an Ohm?

An ohm is a unit of electrical resistance.

Resistance is a physical property that describes opposition to electric current.

The SI system expresses the ohm as:

Ω = V/A

where:

• Ω = ohm
• V = volt
• A = ampere

NIST gives the same relationship: 1 Ω = 1 V/A.

The ohm can also be expressed in terms of SI base units as:

Ω = m² · kg · s⁻³ · A⁻²

The BIPM identifies this as the SI base-unit expression for electrical resistance.

You don’t normally need that longer expression for everyday electronics, but it demonstrates that the ohm is an SI derived unit, not an SI base unit.

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What Does Electrical Resistance Mean?

Imagine trying to push water through two pipes.

A wide pipe allows water to move relatively easily.

A narrow pipe restricts the flow.

Electrical resistance isn’t exactly the same as a pipe, but the analogy can help beginners visualize the idea.

In an electrical circuit:

Higher resistance → less current for a given voltage

Lower resistance → more current for a given voltage

This relationship is described by Ohm’s law.

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What Is Ohm’s Law?

Ohm’s law is one of the fundamental relationships in basic electrical engineering.

The standard equation is:

V = I × R

where:

• V = voltage in volts
• I = current in amperes
• R = resistance in ohms

You can rearrange it to find any of the three quantities:

R = V / I

I = V / R

V = I × R

Example

Suppose a circuit has:

• Voltage = 12 V
• Current = 2 A

Then:

R = 12 / 2

R = 6 Ω

So the circuit’s resistance is 6 ohms.

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What Does Ω Mean on a Multimeter?

If you’ve ever used a digital multimeter, you’ve probably seen the Ω symbol on the dial.

On a multimeter, the Ω setting is used to measure electrical resistance.

You may see a setting such as:

Ω

or ranges such as:

• 200 Ω
• 2 kΩ
• 20 kΩ
• 200 kΩ
• 2 MΩ

The exact ranges depend on the multimeter.

What happens when you measure resistance?

A typical resistance measurement requires the circuit or component to be isolated appropriately, and the meter applies a small test signal to determine resistance.

Important safety rule: Don’t use the resistance setting on a circuit that is energized unless the meter and procedure are specifically designed for that measurement. Follow the multimeter manufacturer’s instructions.

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What Does the Ω Symbol Mean on a Resistor?

If you see something such as:

220 Ω

it means the resistor has a nominal resistance of 220 ohms.

For example:

Marking	Meaning
10 Ω	10 ohms
100 Ω	100 ohms
220 Ω	220 ohms
1 kΩ	1,000 ohms
10 kΩ	10,000 ohms
1 MΩ	1,000,000 ohms

A resistor’s resistance determines how strongly it limits current under the circuit’s operating conditions.

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What Does kΩ Mean?

The letter k means kilo, or one thousand.

Therefore:

1 kΩ = 1,000 Ω

Examples:

2 kΩ = 2,000 Ω

4.7 kΩ = 4,700 Ω

10 kΩ = 10,000 Ω

You’ll frequently see kilohms in electronic circuits.

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What Does MΩ Mean?

The letter M means mega, or one million.

Therefore:

1 MΩ = 1,000,000 Ω

Examples:

2 MΩ = 2,000,000 Ω

4.7 MΩ = 4,700,000 Ω

Megohm values are common when dealing with very high resistance.

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Ohm Prefixes at a Glance

Symbol	Name	Equivalent
mΩ	milliohm	0.001 Ω
Ω	ohm	1 Ω
kΩ	kilohm	1,000 Ω
MΩ	megohm	1,000,000 Ω
GΩ	gigohm	1,000,000,000 Ω

The prefixes allow engineers to describe extremely small or extremely large resistance values without writing long strings of zeros.

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What Is a Milliohm?

A milliohm (mΩ) is one-thousandth of an ohm.

1 mΩ = 0.001 Ω

Milliohm measurements can be important when dealing with very low-resistance connections, cables, busbars, switches, battery connections, and other electrical components where even a small resistance can produce a meaningful voltage drop or power loss at high current.

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What Is a Megohm?

A megohm (MΩ) equals one million ohms.

1 MΩ = 1,000,000 Ω

Very high resistance values appear in applications such as:

• Insulation testing
• High-voltage systems
• Electronic circuits
• Sensors
• Specialized measurement equipment

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What Is the Difference Between Resistance and Impedance?

This is an important distinction.

Resistance is measured in ohms and describes opposition to current associated with resistive behavior.

Impedance is also measured in ohms, but it is the broader concept used in AC circuits and includes resistance plus reactance.

NIST describes the ohm as the SI unit of electrical impedance, and in the direct-current case, electrical resistance.

For basic DC circuits, thinking in terms of resistance is usually enough.

For AC circuits, especially those involving capacitors and inductors, impedance becomes important.

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Resistance vs. Impedance

Feature	Resistance	Impedance
Symbol often used	R	Z
Unit	Ω	Ω
Commonly discussed in	DC and AC circuits	Especially AC circuits
Includes resistance	Yes	Yes
Includes reactance	No	Yes
Depends on frequency	Generally not in the ideal basic model	Often yes

Both are expressed using the ohm.

---

What Is the Difference Between Ω and Ohm?

There is no difference in the unit being represented.

Ohm is the unit’s name.

Ω is its symbol.

For example:

100 ohms = 100 Ω

Similarly:

5 volts = 5 V

2 amperes = 2 A

The BIPM specifies Ω as the unit symbol for the ohm.

---

Who Was Georg Ohm?

The unit is named after Georg Simon Ohm, the German physicist associated with the relationship between electrical potential difference, current, and resistance.

His work became foundational to electrical science.

That’s why the unit is called the ohm rather than simply being named after a Greek letter.

The name honors the scientist, while the symbol Ω provides the internationally recognized shorthand for the unit.

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Why Is the Ohm Named After a Person?

The International System of Units uses several units named after scientists.

Examples include:

• Volt — Alessandro Volta
• Ampere — André-Marie Ampère
• Watt — James Watt
• Ohm — Georg Ohm
• Farad — Michael Faraday
• Hertz — Heinrich Hertz
• Tesla — Nikola Tesla

The BIPM’s SI rules specify that symbols for units derived from proper names use capital letters, which is why the symbols V, A, W, Ω, F, Hz, and T are capitalized.

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When Was the Ohm Officially Recognized?

The history is more complicated than simply saying “the ohm was invented by Georg Ohm.”

Electrical units evolved through international standardization.

The BIPM records that international units for current and resistance were introduced by the International Electrical Congress in Chicago in 1893, with definitions of the international ampere and international ohm confirmed at an international conference in London in 1908.

Later, the international system moved toward absolute electrical units. The CIPM adopted decisions in 1946, and the 9th CGPM approved them in 1948.

The modern SI framework subsequently incorporated the ohm as an SI derived unit.

The current BIPM SI Brochure identifies the ohm, symbol Ω, as the SI derived unit of electrical resistance.

---

Is Ω an SI Unit?

Technically, Ω is the symbol, while ohm is the unit.

The ohm is an SI derived unit.

NIST lists electrical resistance as:

ohm (Ω) = volt/ampere (V/A)

and gives its SI base-unit expression as:

m² · kg · s⁻³ · A⁻².

The BIPM’s SI Brochure likewise lists the ohm among the SI derived units with special names and symbols.

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What Does a High Ohm Reading Mean?

Generally, a higher resistance reading means greater opposition to current.

For example:

10 Ω

has a lower resistance than:

10 kΩ

because:

10 kΩ = 10,000 Ω

But a high reading isn’t automatically “good,” and a low reading isn’t automatically “bad.”

The correct resistance depends on the component and circuit.

For example, a resistor designed to be 10 kΩ should not be judged by the same standard as a heating element designed to have a much lower resistance.

---

What Does a Low Ohm Reading Mean?

A low resistance reading means the measured path offers relatively little resistance to current.

A very low reading may be normal for:

• Heavy-gauge conductors
• Short wires
• Some switches
• Certain motor windings
• Low-resistance components

But a near-zero reading can also indicate a short circuit when the circuit is supposed to have significant resistance.

The expected value matters more than simply asking whether the number is high or low.

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Does 0 Ω Mean No Electricity?

No.

This is a common misunderstanding.

A resistance measurement of approximately 0 Ω means the measured path has very little resistance relative to the meter’s measurement range and accuracy.

It doesn’t mean electricity doesn’t exist.

In an ideal circuit, a perfect conductor could be modeled as having zero resistance, but real-world conductors and measurement systems have nonzero resistance.

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Does Infinite Ω Mean an Open Circuit?

Often, yes.

If a multimeter displays:

• OL
• ∞
• A very large value

while measuring a component or wire that should conduct, the circuit may be open.

An open circuit means there isn’t a complete conductive path for current.

However, the exact display depends on the multimeter.

Always check the meter’s manual.

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What Does Ω Mean in a Circuit Diagram?

In circuit diagrams, resistance is often represented by the letter:

R

while the unit of resistance is:

Ω

For example:

R = 100 Ω

means the resistance value is 100 ohms.

The distinction is:

R = quantity/property

Ω = unit

This is similar to:

V = voltage

V = volt

The same letter can sometimes appear in different contexts, so the surrounding notation matters.

---

What Is the Relationship Between Ohms, Volts, and Amps?

These three quantities are closely connected through Ohm’s law.

V = I × R

So:

Voltage = Current × Resistance

From this:

Resistance = Voltage ÷ Current

and:

Current = Voltage ÷ Resistance

Example

If a component has:

24 V

across it and carries:

3 A

then:

R = 24 ÷ 3 = 8 Ω

So its resistance is 8 ohms.

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Ohm’s Law Triangle

A common educational shortcut is to visualize Ohm’s law as a triangle:

V

I × R

Cover the quantity you’re trying to find.

• Need V? Multiply I × R.
• Need I? Divide V by R.
• Need R? Divide V by I.

It’s a useful memory aid for beginners.

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How Does Resistance Affect Current?

According to Ohm’s law:

I = V/R

If voltage stays constant, increasing resistance decreases current.

For example, with a 12 V source:

2 Ω resistance

I = 12 ÷ 2 = 6 A

4 Ω resistance

I = 12 ÷ 4 = 3 A

12 Ω resistance

I = 12 ÷ 12 = 1 A

So, under this simplified relationship, higher resistance means lower current at the same voltage.

---

What Is the Difference Between Ohms and Watts?

These units measure different things.

Unit	Symbol	Measures
Ohm	Ω	Resistance
Volt	V	Electric potential difference
Ampere	A	Electric current
Watt	W	Power
Coulomb	C	Electric charge
Farad	F	Capacitance
Henry	H	Inductance

Resistance tells you how strongly a circuit element opposes current.

Power tells you how quickly electrical energy is transferred or converted.

---

How Are Ohms Related to Watts?

Ohms and watts are connected through electrical equations.

One useful formula is:

P = I²R

where:

• P = power in watts
• I = current in amperes
• R = resistance in ohms

Another is:

P = V²/R

These relationships are particularly important when selecting resistors because a resistor has both a resistance value and a power rating.

For example, a resistor might be:

1 kΩ, 0.25 W

The 1 kΩ tells you its nominal resistance.

The 0.25 W tells you the power it is designed to dissipate under specified conditions.

---

What Does Ω Mean on a Phone Charger or Power Adapter?

If you see an Ω value in technical specifications for a charger or electronic device, it generally refers to electrical resistance or impedance, depending on the specification.

It doesn’t mean the charger outputs “ohms.”

Chargers are commonly specified using quantities such as:

• Voltage
• Current
• Power
• Frequency

Resistance or impedance may appear in more specialized technical specifications.

---

What Does Ω Mean in Speakers and Headphones?

If you’ve seen specifications such as:

32 Ω

or:

80 Ω

on headphones, that value refers to their nominal impedance.

This is why headphone specifications often say “32 ohms” even though they’re technically describing impedance rather than simple DC resistance.

Common headphone examples

• 16 Ω
• 32 Ω
• 80 Ω
• 250 Ω
• 300 Ω

A higher impedance headphone isn’t automatically better or worse.

The compatibility between the headphones and the source device matters.

---

Why Do Headphones Have Different Ohm Ratings?

Different headphones are designed with different electrical characteristics.

Impedance affects how much voltage and current an audio source needs to drive the headphones to a particular output level.

For that reason:

32 Ω headphones

and

250 Ω headphones

may behave differently when connected to the same source.

The impedance rating is therefore useful when considering amplifier and source compatibility.

---

What Does Ω Mean on a Car?

If you’re seeing Ω in automotive diagnostics, it usually refers to electrical resistance or impedance.

Technicians may use resistance measurements when checking:

• Wires
• Sensors
• Coils
• Motors
• Relays
• Heating elements
• Electrical connections

For example, a service procedure might specify that a component should have a particular resistance range.

A reading far outside the manufacturer’s specification may indicate a fault.

However, automotive diagnosis should always follow the manufacturer’s test procedure because some components must be tested in specific conditions.

---

What Does Ω Mean on a Multimeter When Testing a Wire?

When testing a wire for continuity or resistance, the Ω setting measures the resistance of the electrical path.

A good low-resistance connection may produce a reading close to zero ohms, although the exact number depends on the wire, connections, meter, and test leads.

A very high or overload reading may indicate an open circuit.

Simple example

Suppose you test a short wire and see:

0.3 Ω

That may indicate a low-resistance path.

If you instead see:

OL

the meter may be indicating that it doesn’t detect a conductive path within its measurement range.

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Why Do Multimeter Leads Show Some Resistance?

This surprises many beginners.

When you touch the two meter probes together, you may not see exactly:

0.000 Ω

You might see something like:

0.1 Ω

or another small value.

That’s because the test leads, probe contacts, and internal measurement circuitry have their own resistance.

For low-resistance measurements, technicians may compensate for lead resistance using the meter’s relative/zero function when available.

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Is Ohm a Greek Symbol or a Physics Symbol?

Ω is both a Greek letter and the symbol used for the ohm.

The uppercase Greek letter is called omega.

In physics and engineering, it can also be assigned specialized meanings depending on context.

For example, lowercase omega:

ω

is frequently used for angular frequency.

That’s completely different from the ohm symbol:

Ω

The capitalization matters.

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Ω vs. ω: What’s the Difference?

Symbol	Common identity/use
Ω	Uppercase Greek omega; symbol for ohm
ω	Lowercase Greek omega; often angular frequency

Don’t confuse them.

In electrical engineering:

Ω = ohm

while:

ω = angular frequency

The two symbols look related because they come from the same Greek letter, but they represent different quantities.

---

Does Ω Always Mean Ohms?

No. Context matters.

When Ω appears after a number in an electrical specification, it almost certainly refers to ohms.

For example:

50 Ω

means 50 ohms.

But the character Ω is also the Greek uppercase omega character, and Greek letters can have other uses in mathematics, physics, and engineering.

So:

Ω in an electronics specification → usually ohms

Ω in a Greek-language context → omega

The surrounding context determines the meaning.

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Common Ohm Symbol Mistakes

Mistake 1: Calling Ω “the omega unit”

Ω is the symbol for the ohm.

Omega is the name of the Greek letter.

Mistake 2: Thinking ohms measure electricity itself

Ohms measure resistance, not electricity as a whole.

Mistake 3: Assuming more ohms is always better

The correct resistance depends on the application.

Mistake 4: Confusing Ω with ω

Uppercase Ω represents the ohm in electrical contexts; lowercase ω has different uses.

Mistake 5: Measuring resistance on a powered circuit

This can produce incorrect readings and may damage equipment or create a safety hazard.

Mistake 6: Thinking resistance and impedance are identical

They share the ohm as a unit, but impedance is a broader AC concept.

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Ohm Symbol Quick Reference

Question	Answer
What is the ohm symbol?	Ω
What does Ω stand for?	Ohm
What does an ohm measure?	Electrical resistance
What is 1 Ω equal to?	1 V/A
Who is the unit named after?	Georg Simon Ohm
Is the ohm an SI unit?	Yes, an SI derived unit
What is 1 kΩ?	1,000 Ω
What is 1 MΩ?	1,000,000 Ω
What is the resistance formula?	R = V/I
What is Ohm’s law?	V = IR
Is Ω the Greek letter omega?	Yes, it is the uppercase omega character
Is Ω the same as ω?	No; capitalization and meaning differ

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Frequently Asked Questions About the Ohm Symbol

What does the ohm symbol mean?

The symbol Ω represents the ohm, the SI derived unit of electrical resistance. One ohm equals one volt per ampere.

What is the symbol for ohms?

The standard symbol for ohms is Ω.

Why is Ω used for ohms?

Ω is the uppercase Greek letter omega, adopted as the symbol for the ohm.

Is Ω pronounced omega or ohm?

If you’re reading the symbol as an electrical unit, say “ohm.” The character itself is the uppercase Greek letter omega.

For example:

10 Ω = ten ohms

What does 10 Ω mean?

It means a resistance of 10 ohms.

What does 100 Ω mean?

It means a resistance of 100 ohms.

What does 1 kΩ mean?

It means 1,000 ohms.

What does 1 MΩ mean?

It means 1,000,000 ohms.

What does Ω mean on a multimeter?

It identifies the resistance measurement function, although the exact controls vary by multimeter model.

What does Ω mean on a resistor?

It identifies the resistor’s resistance value.

Is Ω resistance or impedance?

The ohm is the unit for both electrical resistance and impedance. NIST specifically identifies it as the SI unit of electrical impedance and, in the DC case, electrical resistance.

Is ohm an SI unit?

Yes. The ohm is an SI derived unit with the symbol Ω.

What is the formula for ohms?

Using Ohm’s law:

R = V/I

Resistance equals voltage divided by current.

What is 1 ohm equal to?

1 Ω = 1 V/A

One ohm equals one volt per ampere.

Who invented the ohm?

The unit is named after German physicist Georg Simon Ohm, whose work on electrical relationships became foundational to circuit theory.

What does high resistance mean?

High resistance generally means greater opposition to current flow. For a fixed voltage in a simple resistive circuit, higher resistance results in lower current.

What does low resistance mean?

Low resistance means less opposition to current. For a fixed voltage, a lower resistance permits greater current in a simple resistive circuit.

Does 0 ohms mean a short circuit?

It can indicate a short or very low-resistance path, but the meaning depends on what you’re measuring and what resistance the circuit is supposed to have.

Does OL on a multimeter mean infinite resistance?

Usually, OL means the measured resistance is outside the meter’s range or that the circuit is open, depending on the measurement. Check the meter’s manual for its exact meaning.

What is the difference between ohms and volts?

Ohms measure resistance. Volts measure electric potential difference.

What is the difference between ohms and amps?

Ohms measure resistance. Amps measure electric current.

What is the difference between ohms and watts?

Ohms measure resistance. Watts measure power.

What does Ω mean in headphones?

In headphone specifications, Ω usually indicates nominal impedance, not simply DC resistance.

What does Ω mean in electronics?

It generally represents ohms, the unit used for resistance and impedance.

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Final Takeaway: What Does the Ohm Symbol Mean?

The answer is straightforward:

Ω is the symbol for the ohm, the SI unit of electrical resistance.

Resistance describes how strongly a circuit element or material opposes electric current. The basic relationship between voltage, current, and resistance is given by Ohm’s law: V = IR.

One ohm is defined by the relationship:

1 Ω = 1 V/A

The symbol looks like the Greek letter omega because Ω is the uppercase omega character, but when it appears as an electrical unit, you read it as ohm, not simply “omega.” The BIPM and NIST both identify Ω as the symbol for the ohm.

You’ll encounter the symbol on:

• Resistors
• Multimeters
• Circuit diagrams
• Automotive diagnostic equipment
• Headphones and speakers
• Electronic components
• Electrical test equipment
• Engineering specifications

Once you understand Ω = ohm = resistance, the symbol becomes much easier to recognize.

And the next time you see 4.7 kΩ, 32 Ω, or 1 MΩ, you’ll know exactly what that number is telling you.

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