A cap stores power.
It holds tiny bits of energy. It helps things like radios work. This part is in many tools you use. It can even be in the sky!
Can you find one in your house?
A cap stores tiny bits of power.
It has two metal surfaces inside. These surfaces do not touch. A special material sits between them. This material helps hold more power.
When you add power, the energy stays inside. It can then be used later. This is like how clouds work. Clouds hold power in the sky. This can cause bright lightning!
Many tools use these parts to work well.
A capacitor is a tool that stores electrical energy.
It has two metal surfaces that are very close. These surfaces do not touch. A material sits between them. This material is called a dielectric.
The dielectric does not let electricity flow through it. Instead, it helps the device hold more charge.
When you connect a capacitor to a battery, something happens. An electric field grows between the two surfaces. This causes positive charge to gather on one plate. Negative charge gathers on the other plate.
This is like a water pipe with a stretchy skin inside. The water cannot pass through the skin. But the skin stretches to hold the pressure.
People first made these in the 1740s. They used glass jars filled with water. These were called Leyden jars.
Today, we use many types. Some use paper or plastic film. Others use ceramic or even air. Capacitors help radios work. They also help computers store memory. Even clouds in the sky act like natural capacitors!
A capacitor is a clever tool used to store electrical energy.
It is a passive component, which means it does not create energy on its own. Instead, it holds onto electric charges for later use. Most capacitors have two terminals to connect them to a circuit.
They are often called "caps" for short. In the past, people called them condensers. This name is still used sometimes for specific tools like microphones. The amount of energy a capacitor can hold depends on its capacitance.
How does a capacitor actually work?
It usually has two metal surfaces, called conductors, placed very close together. Between these surfaces is a material called a dielectric. This dielectric is an insulator, so electricity cannot flow through it. When you connect the capacitor to a battery, an electric field develops. This field pulls positive charges to one plate and negative charges to the other.
It is like a stretchy skin inside a water pipe. Water cannot pass through the skin, but the pressure makes it stretch. This stretching allows the device to hold onto the electrical pressure.
People have been studying this for a long time. In the 1740s, experimenters found they could store charge in glass jars filled with water. These were called Leyden jars.
In 1745, Ewald Georg von Kleist discovered this in Germany. A year later, Pieter van Musschenbroek invented a similar jar in the Netherlands. Benjamin Franklin later studied these jars and learned a big secret. He realized the charge was actually stored on the glass, not in the water. He also began using the word "battery" to describe a group of these units.
Capacitors come in many different shapes and sizes today.
Some use paper, while others use plastic film or ceramic. In 1909, William Dubilier invented mica capacitors. Later, in 1896, Charles Pollak patented an electrolytic capacitor using aluminum. These modern versions are much smaller than the old glass jars. In 1966, Dr. Robert Dennard created the modern DRAM architecture. This uses a special MOS capacitor to help computers store memory.
This allows your devices to remember information very quickly.
You can find capacitors working in many places around you. They help radios tune into the right stations. They also help power supplies stay steady by smoothing out the electricity. In large power systems, they help keep the flow of energy stable. You can even see a natural version of this in the sky.
Clouds and the Earth act like a giant capacitor. The air between them acts as the dielectric. When the charge builds up too much, it creates a bolt of lightning!
A capacitor is a passive electronic component designed to store electrical energy.
It works by accumulating electric charges on two closely spaced surfaces that are insulated from one another. This ability to hold a charge is known as capacitance. While any two conductors near each other in a circuit possess some capacitance, a capacitor is a component built specifically to add a controlled amount of capacitance to a circuit.
The utility and function of the device depend entirely on its specific capacitance value. Historically, these devices were often called condensers. This term is still used in certain contexts, such as in the name of a condenser microphone.
To understand the mechanism, imagine two electrical conductors, such as metallic plates, separated by a non-conducting material. This material is called a dielectric.
Common dielectric materials include glass, ceramic, plastic film, paper, mica, air, or even oxide layers. When a voltage, or electric potential difference, is applied across the capacitor's terminals, an electric field develops across the dielectric. This field causes a net positive charge to collect on one plate and a net negative charge to collect on the other.
Crucially, no current actually flows through a perfect dielectric. Instead, there is a flow of charge through the source circuit. If the voltage is applied long enough, the current in the source circuit will eventually cease once the capacitor is charged.
Capacitors can be understood through a hydraulic analogy to visualize how they handle energy.
In this comparison, voltage is like water pressure, and electrical current is like water flowing through a pipe. A capacitor acts like an elastic diaphragm placed inside that pipe. While water cannot pass through the diaphragm, the pressure causes it to stretch or un-stretch. In an alternating current (AC) circuit, the diaphragm allows charge to move back and forth on both sides, even though no electrons cross the barrier. In a direct current (DC) circuit, the capacitor acts like a hydraulic accumulator, storing energy until the pressure is released.
There are many different types of capacitors used in modern technology.
Early versions used flat glass plates alternating with foil conductors. As the need for radio technology grew around 1900, engineers required more compact designs. They began using flexible dielectric sheets, such as oiled paper, sandwiched between metal foils and rolled into small packages. Other types include ceramic capacitors, which use porcelain, and mica capacitors, which were invented by William Dubilier in 1909. Electrolytic capacitors were also developed; Charles Pollak patented an aluminum version in 1896. Today, we also use supercapacitors, which were invented in 1957 using porous carbon electrodes to achieve extremely high capacity.
The history of the capacitor began in the 1740s with the discovery of the Leyden jar.
In 1745, Ewald Georg von Kleist found that charge could be stored in a glass jar filled with water. A year later, Pieter van Musschenbroek invented a similar device named after the University of Leiden. Benjamin Franklin later investigated these jars and reached a vital conclusion. He discovered that the charge was actually stored on the glass rather than in the water. Franklin also introduced the term "battery" to describe a row of these units used together to increase power.
Capacitors serve many essential roles in electrical systems. In analog filter networks, they are used to smooth the output of power supplies. In resonant circuits, they allow radios to tune into specific frequencies. They are also vital in electric power transmission systems to stabilize voltage and power flow.
In the world of computing, capacitors have been used for dynamic memory. Modern DRAM utilizes the property of energy storage in capacitors to function. Specifically, in 1966, Dr. Robert Dennard invented the modern DRAM architecture, which combines a single MOS transistor with a capacitor for each memory cell.
Nature also demonstrates the principles of capacitance on a massive scale. The most common natural example is the accumulation of static charges between clouds in the sky and the surface of the Earth. In this massive natural system, the air between the clouds and the ground serves as the dielectric. When the electrical pressure reaches a point where the breakdown voltage of the air is exceeded, the stored energy is released. This sudden discharge results in the bolts of lightning we see during storms.
Where will your curiosity go next?
🖼️ Images & Media (25)
+ 13 more
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.