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Physics for Kids

Resistors, Capacitors, and Inductors

The three basic elements used in electronic circuits are the resistor, capacitor, and inductor. They each play an important role in how an electronic circuit behaves. They also have their own standard symbols and units of measurement.


A resistor represents a given amount of resistance in a circuit. Resistance is a measure of how the flow of electric current is opposed or "resisted." It is defined by Ohm's law which says the resistance equals the voltage divided by the current.

Resistance = voltage/current
R = V/I

Resistance is measured in Ohms. The Ohm is often represented by the omega symbol: Ω.

The symbol for resistance is a zigzag line as shown below. The letter "R" is used in equations.

Resistor Symbol


A capacitor represents the amount of capacitance in a circuit. The capacitance is the ability of a component to store an electrical charge. You can think of it as the "capacity" to store a charge. The capacitance is defined by the equation

C = q/V
where q is the charge in coulombs and V is the voltage.

In a DC circuit, a capacitor becomes an open circuit blocking any DC current from passing the capacitor. Only AC current will pass through a capacitor.

Capacitance is measured in Farads.

The symbol for capacitance is two parallel lines. Sometimes one of the lines is curved as shown below. The letter "C" is used in equations.

Capacitor Symbol


An inductor represents the amount of inductance in a circuit. The inductance is the ability of a component to generate electromotive force due to a change in the flow of current. A simple inductor is made by looping a wire into a coil. Inductors are used in electronic circuits to reduce or oppose the change in electric current.

In a DC circuit, an inductor looks like a wire. It has no affect when the current is constant. Inductance only has an effect when the current is changing as in an AC circuit.

Inductance is measured in Henrys.

The symbol for inductance is a series of coils as shown below. The letter "L" is used in equations.

Inductor Symbol

Interesting Facts about Resistors, Capacitors, and Inductors

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More Electricity Subjects

Circuits and Components
Intro to Electricity
Electric Circuits
Electric Current
Ohm's Law
Resistors, Capacitors, and Inductors
Resistors in Series and Parallel
Conductors and Insulators
Digital Electronics
Other Electricity
Electricity Basics
Electronic Communications
Uses of Electricity
Electricity in Nature
Static Electricity
Electric Motors
Glossary of Electricity Terms

Science >> Physics for Kids

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