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Resistor

physical science Maturity 11-13

A resistor helps control power. It can slow down the flow. It is in many machines. It helps things work well. It can even get warm.

Carbon and ceramic resistors of different power ratings.jpg
Carbon and ceramic resistors of different power ratings.jpg
Do you see them in toys?

40 words

A resistor is a tiny part in machines.

Carbon and ceramic resistors of different power ratings.jpg
Carbon and ceramic resistors of different power ratings.jpg
It helps control how much power flows.

Think of water in a pipe. A resistor is like hair in that pipe. The hair slows the water down. A resistor does the same to electricity. It slows the flow of power.

ResistanceHydraulicAnalogy2.svg
ResistanceHydraulicAnalogy2.svg

Some resistors stay the same. Others can change. You might use one to change volume. You can also use one to dim a light.

When power flows through, it can get warm. This can turn into heat. Some big ones need to stay cool.

Resistors are in almost all electronic tools. They help our gadgets work right.

114 words

A resistor is a tiny part in a circuit.

Carbon and ceramic resistors of different power ratings.jpg
Carbon and ceramic resistors of different power ratings.jpg
Its main job is to control the flow of electricity. You can think of it like water in a pipe. If a pipe is clogged with hair, the water flows slowly. A resistor works in a similar way. It makes it harder for the electric current to flow.
ResistanceHydraulicAnalogy2.svg
ResistanceHydraulicAnalogy2.svg

Scientists measure this resistance in units called ohms. The symbol for an ohm is Ω. Some resistors are fixed. This means their resistance stays the same. Other resistors are variable. These can change their resistance. You might use a variable resistor to turn a volume knob.

Potentiometer cutaway drawing.png
Potentiometer cutaway drawing.png

When electricity flows through a resistor, it makes heat. This is called power dissipation. Some resistors are very big to handle a lot of heat. If a resistor gets too hot, it can break or even start a fire.

Danotherm HS50 power resistor.jpg
Danotherm HS50 power resistor.jpg
Because of this, engineers must pick the right size for every job. Resistors are found in almost all electronic tools today.

179 words

A resistor is a tiny but vital part of an electronic circuit.

Carbon and ceramic resistors of different power ratings.jpg
Carbon and ceramic resistors of different power ratings.jpg
Its main job is to provide electrical resistance. This means it limits how much electricity can flow through a path. Engineers use them to reduce current or adjust signal levels. They can also divide voltages or protect other parts of a device. Resistors are found in almost all electronic equipment today.
3 Resistors.jpg
3 Resistors.jpg

You can picture how a resistor works by thinking about water. Imagine water flowing through a pipe in a house.

ResistanceHydraulicAnalogy2.svg
ResistanceHydraulicAnalogy2.svg
If that pipe gets clogged with hair, the water flows much slower. It takes more pressure to push the water through the clog. Electricity works in a similar way. Pushing current through a large resistance is like pushing water through a clogged pipe. It requires a larger push, called voltage, to keep the current moving.
Resistor symbol America.svg
Resistor symbol America.svg

Scientists use a rule called Ohm's law to understand this relationship. This law says that the voltage across a resistor is proportional to the current passing through it. The constant number that connects them is the resistance.

Resistor symbol Europe.svg
Resistor symbol Europe.svg
We measure this resistance in units called ohms, shown by the symbol Ω. This unit is named after Georg Simon Ohm. For very small or very large values, we use prefixes. We might use milliohms for tiny amounts or megohms for huge ones.
ResistorColorCodeGuide.jpg
ResistorColorCodeGuide.jpg

There are different ways to connect resistors together in a network. If you connect them in a series, they sit end to end. The total resistance is just the sum of all their individual values.

resistors in series.svg
resistors in series.svg
If you connect them in parallel, they sit side by side. This works differently because the total resistance is calculated using reciprocals.
resistors in parallel.svg
resistors in parallel.svg
Some networks are very complex and mix both types of connections. Engineers use special math to solve these tricky circuit puzzles.

When electricity flows through a resistor, it turns into heat.

Resistor warming thermal video.webm
Resistor warming thermal video.webm
This is called power dissipation. If a resistor handles too much power, it can get very hot. This heat might damage the part or even cause a fire.
Danotherm HS50 power resistor.jpg
Danotherm HS50 power resistor.jpg
Some resistors are built to be flameproof to stay safe. Older styles, like carbon composition resistors, were common in the 1960s.
Old Radio Resistors.jpg
Old Radio Resistors.jpg
Today, we use many different types of resistors for all kinds of jobs.

403 words

A resistor is a passive, two-terminal electronic component. It works by implementing electrical resistance within a circuit.

Carbon and ceramic resistors of different power ratings.jpg
Carbon and ceramic resistors of different power ratings.jpg
This component is essential for managing how electricity behaves. Engineers use resistors to reduce current flow or adjust signal levels. They also use them to divide voltages or bias active elements. Resistors are ubiquitous, meaning they are found everywhere in electronic equipment.
3 Resistors.jpg
3 Resistors.jpg

To understand how a resistor works, we can use the hydraulic analogy. Imagine water flowing through a system of pipes.

ResistanceHydraulicAnalogy2.svg
ResistanceHydraulicAnalogy2.svg
If a pipe becomes clogged with hair, the water flows more slowly. It requires much higher pressure to maintain the same flow through the clog. Electricity behaves in a very similar way. Pushing current through a large resistance is like pushing water through a clogged pipe. It requires a larger push, known as voltage, to drive the same amount of electric current.

Scientists use Ohm's law to describe this relationship mathematically. This law states that the voltage across a resistor is proportional to the current passing through it. The constant of proportionality is the resistance itself.

Resistor symbol America.svg
Resistor symbol America.svg
The standard unit for electrical resistance is the ohm, represented by the symbol Ω. This unit is named after the scientist Georg Simon Ohm. Because resistors cover a massive range of values, we use derived units. These include the milliohm (1 mΩ) for small values and the megohm (1 MΩ) for very large ones.
Resistor symbol Europe.svg
Resistor symbol Europe.svg

Resistors can be organized into different types of networks. In a series connection, resistors are placed end to end. The total resistance of a series circuit is the sum of each individual resistance value.

resistors in series.svg
resistors in series.svg
In a parallel connection, resistors are placed side by side. The total resistance in parallel is calculated as the reciprocal of the sum of the reciprocals of the individual resistors.
resistors in parallel.svg
resistors in parallel.svg
Some networks combine both series and parallel connections. These complex networks may require sophisticated methods like the Y-Δ transform to solve.

When current flows through a resistor, electrical energy is converted into heat. This process is called power dissipation.

Resistor warming thermal video.webm
Resistor warming thermal video.webm
The power consumed is calculated by multiplying the voltage by the current. If a resistor's average power dissipation exceeds its maximum rating, it may suffer permanent damage. This can change its resistance or even cause the component to burn.
Danotherm HS50 power resistor.jpg
Danotherm HS50 power resistor.jpg
Excessive heat can also damage the circuit board or start a fire. To prevent this, some engineers use flameproof resistors that will not produce flames during an overload.

There are many different physical types of resistors. Fixed resistors have a resistance that stays mostly constant regardless of temperature or time. Variable resistors can be adjusted, such as a volume control or a lamp dimmer.

Potentiometer cutaway drawing.png
Potentiometer cutaway drawing.png
One historical type is the carbon composition resistor. These consist of a mixture of powdered carbon and an insulating material like ceramic.
Old Radio Resistors.jpg
Old Radio Resistors.jpg
While they can withstand high overloads, they are less popular today because they lack stability. They can also change value if they are exposed to high humidity or heat during soldering.

Resistors are also categorized by their form factor and mounting style. Some components are axial, meaning their leads come off the body in a straight line. Others are radial, with leads coming off the sides.

3 Resistors.jpg
3 Resistors.jpg
Modern electronics often use Surface Mount Technology (SMT) for very small components. Resistors are also found inside integrated circuits rather than as separate parts. Whether they are large power resistors or tiny surface-mount parts, they are the foundation of modern electrical systems.

604 words
🖼️ Images & Media (23)
File:Resistor symbol America.svg
Resistor symbol America.svg
File:Resistor symbol Europe.svg
Resistor symbol Europe.svg
File:Carbon and ceramic resistors of different power ratings.jpg
Carbon and ceramic resistors of different...
File:ResistanceHydraulicAnalogy2.svg
ResistanceHydraulicAnalogy2.svg
File:resistors in series.svg
resistors in series.svg
File:resistors in parallel.svg
resistors in parallel.svg
Resistor warming thermal video.webm
File:Danotherm HS50 power resistor.jpg
Danotherm HS50 power resistor.jpg
File:USSR power resistor VZR 12W.JPG
USSR power resistor VZR 12W.JPG
File:Sil resistor.png
Sil resistor.png
File:3 Resistors.jpg
3 Resistors.jpg
File:Résistances anciennes annees 50.jpg
Résistances anciennes annees 50.jpg

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