In this video David explains why physicists came up with the idea of the electric field, how it's useful, and explains how the electric field is defined. Created by David SantoPietro.
The direction of an electrical field at a point is the same as the direction of the electrical force acting on a positive test charge at that point. For example if you place a positive test charge in an electric field and the charge moves to the right you know the direction of the electric field in that region points to the right. Created by David SantoPietro.
Sal shows that there will be a net torque on a loop of current in a wire. Sal shows that this net torque will cause the loop to rotate. Created by Sal Khan.
Sal shows that a commutator can be used in order to keep the loop of wire rotating in the magnetic field. Created by Sal Khan.
Sal finishes the explanation of how a commutator will allow a loop of wire to continue spinning in a magnetic field, thereby allowing it to work as an electric motor. Created by Sal Khan.
David explains electric potential (voltage). Created by David SantoPietro.
In this video David explains how to find the electric potential energy for a system of charges and solves an example problem to find the speed of moving charges. To see the calculus derivation of the formula watch this video. Created by David SantoPietro.
In this video David shows how to find the total electric potential at a point in space due to multiple charges. Created by David SantoPietro.
In this video David derives the formula to find the power used by a resistor. Created by David SantoPietro.
Students will investigate the characteristics of electromagnetism and then use what they learn to plan and conduct an experiment on electromagnets.
Students learn about the scientific and mathematical concepts around electromagnetic light properties that enable the engineering of sunglasses for eye protection. They compare and contrast tinted and polarized lenses as well as learn about light intensity and how different mediums reduce the intensities of various electromagnetic radiation wavelengths. Through a PowerPoint® presentation, students learn about light polarization, transmission, reflection, intensity, attenuation, and Malus’ law. A demo using two slinky springs helps to illustrate wave disturbances and different-direction polarizations. As a mini-activity, students manipulate slide-mounted polarizing filters to alter light intensity and see how polarization by transmission works. Students use the Malus’ law equation to calculate the transmitted light intensity and learn about Brewster’s angle. Two math problem student handouts are provided. Students also brainstorm ideas on how sunglasses could be designed and improved, which prepares them for the associated hands-on design/build activity.
Introduction to electromagnetic waves and the electromagnetic spectrum.
This is a description of a student experiment that teachers can adapt to allow students to prove that electric current produces a magnetic field. The sample includes a specific example of how to do the experiment which can be adapted to an inquiry investigation by having students complete the initial experiment and then write their investigation question and further investigate the phenomena. When completing this as a demonstration or student experiment batteries can be substituted for the variable power supply if power supplies are not available or convenient to use. The voltage provided to the circuit can be easily manipulated by changing the number of batteries connected.
In this animation produced by WGBH and Digizyme, Inc., see how molecules of DNA are separated using gel electrophoresis, and how this process enables scientists to compare the molecular variations of two or more DNA samples.
This resource from the AMERICAN EXPERIENCE Web site, which contains both an interactive activity and illustrated text, looks at the composition of different types of steel and their impact on technology.
An emf induced by motion relative to a magnetic field is called a motional emf. This is represented by the equation emf = LvB, where L is length of the object moving at speed v relative to the strength of the magnetic field B.
Using Balmer-Rydberg equation to solve for photon energy for n=3 to 2 transition. Solving for wavelength of a line in UV region of hydrogen emission spectrum. Created by Jay.
Students learn to apply the principles and concepts associated with energy and the transfer of energy in an engineering context by designing and making musical instruments. They choose from a variety of provided supplies to make instruments capable of producing three different tones. After completing their designs, students explain the energy transfer mechanism in detail and describe how they could make their instruments better.
Demos and activities in this lesson are intended to illustrate the basic concepts of energy science -- work, force, energy, power etc. and the relationships among them. The "lecture" portion of the lesson includes many demonstrations to keep students engaged, yet has high expectations for the students to perform energy related calculations and convert units as required. A homework assignment and quiz are used to reinforce and assess these basic engineering science concepts.
Students search for clues of energy around them. They use what they find to create their own definition of energy. They also relate their energy clues to the engineering products they encounter every day.