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New videos from Khan Academy 2021-04-12T17:29:53.000000
Atualizado: 1 hora 56 minutos atrás

The U.S. Civil War, sharpshooters, and Winslow Homer

seg, 2021-04-12 17:29
Winslow Homer, The Army ofthe Potomac—A Sharpshooter on Picket Duty, 1862, wood engraving on paper, 23.2 x 35.1 cm, illustration in Harper’s Weekly, November 15, 1862 (Smithsonian American Art Museum). Speakers: Sarah Alvarez and Dr. Kimberly Kutz Elliott

Max Ernst, Two Children Are Threatened by a Nightingale

qua, 2021-04-07 17:53
Max Ernst, Two Children Are Threatened by a Nightingale, 1924, oil with painted wood elements and cut-and-pasted printed paper on wood with wood frame, 69.8 x 57.1 x 11.4 cm (The Museum of Modern Art, New York) With Dr. Steven Zucker and Dr. Beth Harris

Whistler, Nocturne in Black and Gold, the Falling Rocket

qui, 2021-04-01 20:15
James Abbott McNeill Whistler, Nocturne in Black and Gold, the Falling Rocket, 1875, oil on panel, 60.3 × 46.7 cm (Detroit Institute of Arts) A conversation with Dr. Steven Zucker and Dr. Beth Harris

Volume density

qui, 2021-04-01 19:38
Volume density is the amount of a quantity (often mass) per unit of volume. Density=Quantity/Volume

Area density

qui, 2021-04-01 19:38
Area or surface density is the amount of a quantity (often mass) per unit of area. Density=Quantity/Area

Subtracting with place value blocks (regrouping)

qua, 2021-03-31 17:56
Sal uses place value blocks to regroup and subtract 438-272.

Mickalene Thomas on Her Materials and Artistic Influences

sex, 2021-03-26 20:36
By art21. Artist Mickalene Thomas discusses her use of craft materials, her artistic influences, and the importance of seeing oneself represented in museums.

Carrie Bethel, Basket bowl

sex, 2021-03-26 17:09
Join Gaylord Torrence and Brian Vallo for a closer look at, and in-depth commentary on, a selection of highlights in the exhibition Art of Native America: The Charles and Valerie Diker Collection. Featuring Gaylord Torrence, Fred and Virginia Merrill Senior Curator of American Indian Art, The Nelson Atkins Museum of Art Basket Bowl The exhibition is made possible by The Peter Jay Sharp Foundation, the Diane W. and James E. Burke Fund, the Enterprise Holdings Endowment, and the Walton Family Foundation. The Metropolitan Museum of Art is situated in Lenapehoking, the homeland of Lenape peoples, and respectfully acknowledges their ongoing cultural and spiritual connections to the area. Credits Editor: Sarah Cowan Producer: Melissa Bell Audio: David Raymond Photography: Eileen Travell Music: Austin Fisher. Archival images Carrie Bethel, Courtesy Yosemite National Park Archives, Museum, and Library © 2018 The Metropolitan Museum of Art

Michelozzo, Palazzo Medici

qua, 2021-03-24 19:11
Michelozzo, Palazzo Medici, Florence, begun 1444 A conversation with Dr. Steven Zucker and Dr. Beth Harris

Manuel Vilar, Tlahuicole

qua, 2021-03-24 18:53
Manuel Vilar, Tlahuicole, the Tlaxcaltecan General, Fighting in the Gladiatorial Sacrifice, 1851, plaster, 216 cm high (Museo Nacional de Arte, Mexico City) A conversation between Dr. Lauren Kilroy-Ewbank and Dr. Steven Zucker

Electric pot.: Where is potential (energy) more?

ter, 2021-03-23 09:44
Since positive chargers accelerate along the field direction, they gain kinetic energy or lose potential energy. So, potential always reduces along the field lines. Negative charges, however, will accelerate against the field lines and lose potential energy along the opposite direction of the field lines.

Electric potential & work

ter, 2021-03-23 09:44
The potential at a point can be calculated as the work done by the field in moving a unit positive charge from that point to the reference point - infinity. You can also calculate the potential as the work done by the external force in moving a unit positive charge from infinity to that point without acceleration.

Electric pot. : Find sign of work done

ter, 2021-03-23 09:44
To find the sign of work done, check if the direction of the force and the displacement are the same or not. If they are in the same direction, work is positive, else it's negative. When moved slowly, work done by an external force on a charge is always in the opposite direction of work done by the electric force.

Equipotential surfaces of two charges (& dipoles)

ter, 2021-03-23 09:44
Let's explore how the equipotential surfaces look like for two, like and unlike charges, kept close to each other.

Dipole potential: Numerical

ter, 2021-03-23 09:44
Let's calculate potential far away from tiny dipoles.

Calculating E from V(x,y,z): E = - potential gradient

ter, 2021-03-23 09:44
Let's calculate the electric field vector by calculating the negative potential gradient. We first calculate individually calculate the x,y,z component of the field by partially differentiating the potential function.

Equipotential surfaces (& why they are perpendicular to field)

ter, 2021-03-23 09:44
Equipotential surfaces have equal potentials everywhere on them. For stronger fields, equipotential surfaces are closer to each other! These equipotential surfaces are always perpendicular to the electric field direction, at every point.

Potential diff. & negative potentials

ter, 2021-03-23 09:44
The potential at any point is always an indicator of how much more potential energy a coulomb would have compared to when it's at some reference point. So, if the potential is negative, it means the coulomb at that point would have less potential energy compared to when it's at the reference point. Hence potential at a point is always the potential difference between that point and some reference.

Relation between electric field & potential

ter, 2021-03-23 09:44
Electric fields can also be thought of a negative potential gradient. In this video, let's explore the meaning of this statement.

Conductor with charge inside a cavity

ter, 2021-03-23 09:44
Consider a charge q, inside a cavity of a spherical conductor. Let's explore how the induced charges get redistributed in electrostatic conditions.


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