Introduction to Capacitors

Demonstrates basic function and includes information on calculating the capacitance of parallel and series configurations.

 

Parallel RC circuits

US Department of Defense 1972-01-01

 Reviews the operation of parallel RC circuit and specifically points out how to solve for branch currents and total impedance by using ohm's law. Reviews vector representations and show how approximate total current and phase angle are found by measuring the vectors. Introduces trigonometric functions used to solve for total impedance, total current, phase angle, and power factor. Concludes with a brief review of apparent and true power and their relationship to the power factor.

 

Series RC Circuits

US Department of Defense 1972 Reviews the use of vector analysis, pythagorean theorem, and trogonometric functions as applied to a series RC ciruit. Graphically illustrates the consruction of the impedance and voltage vector. Shows use of Ohm's law for AC to solve for unknown circuit parameters. Uses an oscilloscope to demonstrate phase relationships and relative amplitudes.

 

Voltage Doublers

US Department of Defense - 1970-01-01

Explains the theory of operation of a voltage doubler. Traces charge and discharge paths for the capacitors. Determines peak output voltage and ripple frequency.

 

MAKE Presents: The Capacitor

Simple yet effective, they come in a dizzying array of forms and materials. Vital to so many circuits for storage, timing, and filtration – the mighty capacitor!

 In this installment of the MAKE presents series Collin Cunningham explains how to build a leyden jar, how the capacitor was invented, and how to use one to light an LED.

 

Exploding Wire

A 100uF capacitor is charged to 3kV (450 joules) and then discharged through a thin iron wire, causing it to explode.

 

MIT 8.02 Electricity and Magnetism Lecture 24

MIT 8.02 Electricity and Magnetism, Spring 2002

Professor Walter Lewin

Transformers, car coils,  RC Circuits

Other lectures from the same course

Voltage doublers

From the United States Department of Defense.  Explains the theory of operation of a voltage doubler.  Traces charge an discharge paths for the capacitors.  Determines peak output voltage and ripple frequency.

Science off the Sphere: 1.21 Legowatts

NASA Astronaut Don Pettit gets creative with an educational LEGO kit aboard the International Space Station. Answer the challenge question at www.physicscentral.com/sots for a chance for prizes!

Other Science off the Sphere videos

Weekend Projects - Solar Joule Bracelet

The Solar Joule Bracelet combines two separate projects, a solar battery and a "joule thief," to build a wearable circuit that powers an LED. Solar energy flows through the photodiodes, building up a supercapacitor, which essentially acts like a battery. This energy is then delivered to the joule thief, where oscillations eventually exceed the LED's forward voltage, making it light up. Once fully charged, these oscillations will occur so fast that the LED will appear continuously bright, visible even during daytime!

 Complete instructions

 

MIT 8.02 Electricity and Magnetism Lecture 14

MIT 8.02 Electricity and Magnetism, Spring 2002

Professor Walter Lewin

Biot-Savart Law, the Leyden Jar revisited, high-voltage power lines.

Other lectures from the same course

Theremin - Sixty Symbols

If ever a musical instrument was designed for physicists, it was this one.

Other Sixty Symbols videos

MIT 8.02 Electricity and Magnetism Lecture 12

MIT 8.02 Electricity and Magnetism, Spring 2002

Professor Walter Lewin

Review before exam:  Gauss's Law, Capacitor, Kirchoff's Laws, Ohm's Law

Other lectures from the same course

MIT 8.02 Electricity and Magnetism Lecture 8

MIT 8.02 Electricity and Magnetism, Spring 2002

Professor Walter Lewin

Capacitors, dielectrics, Van de Graaff generator.

Other lectures from the same course

MIT 8.02 Electricity and Magnetism Lecture 7

MIT 8.02 Electricity and Magnetism, Spring 2002

Professor Walter Lewin

Capacitance and field energy.

Other lectures from the same course

How a Capacitor Works - by Dr. Oliver Winn

Diagrams, graphics with explanation by Dr. Oliver Winn - pioneer in GE's capacitor and battery technologies. Electrolytic and Dielectric Capacitors explained, how its made using polypropylene. electrons enter the top plate creating a negative charge, this repels electrons in the bottom plate, energy is stored in the dielectric via the field. Dr. Winn worked in Fort Edward/Hudson Falls and Columbia, South Carolina GE plants. His work improved the efficiency of capacitors by 3x while reducing production cost. They made their own aluminum foil and plastics.

Charge and discharge of a capacitor

A capacitor is charged by a battery: the charge Q increases, but the current I decreases (at first, the charges move fast; at the end, they move slowly).

When the capacitor is discharged through a resistor: the charge Q and the current I both decrease (at first, the charges move fast; at the end, they move slowly).

Other animations by Yves Pelletier

Make your own capacitor

2 sheets of aluminium foil separated with saran wrap.