An explanation of cryptographic proof-of-work protocols, which are used in various cryptographic applications and in bitcoin mining. Created by Zulfikar Ramzan.

The mechanisms by which the supply of bitcoins is controlled. Created by Zulfikar Ramzan.

A detailed explanation of what makes bitcoin transaction block chains secure. Created by Zulfikar Ramzan.

The mechanics of a bitcoin transaction block chain, which is a construct that is generated by bitcoin miners and functions as a global ledger for recording and validating bitcoins. Created by Zulfikar Ramzan.

The basic mechanics of a bitcoin transaction between two parties and what is included within a given bitcoin transaction record. Created by Zulfikar Ramzan.

Bit-zee is a project designed to inspire students to explore math and science. It was created from everyday items (a hair dryer, tap light, alarm clock, digital camera, and a universal remote). See the following link for help with the code https://sites.google.com/site/khanacademyprojects/home. Created by Karl Wendt.

Describe a bivariate relationship's linearity, strength, and direction. In other words, plotting things that take two variables into consideration and trying to see whether there's a pattern with how they relate.

Learn about the naval warfare between Britain and Germany that led to the sinking of the Lusitania. Created by Sal Khan.

Learn about the naval warfare between Britain and Germany that led to the sinking of the Lusitania. Created by Sal Khan.

This art history video discussion looks at Arnold Bocklin's "Self-Portrait with Death Playing the Fiddle", 1872, oil on canvas, 75 x 61 cm (Alte Nationalgalerie, Berlin).

This art history video discussion looks at Bodhisattva, probably Avalokiteshvara (Guanyin), Northern Qi dynasty, c. 550--60, Shanxi Province, China, sandstone with pigments, 13-3/4 feet / 419.1 cm high (Metropolitan Museum of Art, New York).

Calculating electron energy for levels n=1 to 3. Drawing a shell model diagram and an energy diagram for hydrogen, and then using the diagrams to calculate the energy required to excite an electron between different energy levels. Created by Jay.

Using classical physics to calculate the energy of electrons in Bohr model. Solving for energy of ground state and more generally for level n. Created by Jay

Using equation for Bohr model radii to draw shell model for n=1 to 3, and calculating the velocity of a ground state electron. Created by Jay

Using classical physics and vectors, plus assumption that angular momentum of electron is quantized, to derive the equation for Bohr model radii. Created by Jay.

Learn about the difference between stocks and bonds. Topics include the key characteristics that define an asset as a bond vs. a stock. Created by Sal Khan.

This art history video discussion looks at Rosa Bonheur's "Plowing in the Nivernais (or The First Dressing)", oil on canvas, 1849 (Musee d'Orsay, Paris).