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In this video David derives the formula to find the power used by a resistor. Created by David SantoPietro.
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Physics on Khan Academy: Physics is the study of the basic principles that govern the physical world around us. We'll start by looking at motion itself. Then, we'll learn about forces, momentum, energy, and other concepts in lots of different physical situations. To get the most out of physics, you'll need a solid understanding of algebra and a basic understanding of trigonometry.
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This video gives a little bit of background for carbon-13 NMR, including the use of TMS and deuterated solvents (more on both of those are covered in the proton NMR video), followed by how to interpret carbon-13 spectra.
Generator is a machine that converts mechanical energy into electrical energy. It works based on principle of faraday law of electromagnetic induction. The faradays law states that whenever a conductor is placed in a varying magnetic field, EMF is induced and this induced EMF is equal to the rate of change of flux linkages. This EMF can be generated when there is either relative space or relative time variation between the conductor and magnetic field.
These are also called as alternators. It is the most important means of producing electrical power in many of the places since now days all the consumers are using AC. It works based on principle of the electromagnetic induction. These are of two types one is induction generator and other one is synchronous generator. The induction generator requires no separate DC excitation, regulator controls, frequency control or governor. This concept takes place when conductor coils turn in a magnetic field actuating a current and a voltage. The generators should run at a consistent speed to convey a stable AC voltage, even no load is accessible.
DC Generators: -
DC generator is typically found in off-grid applications. These generators give a seamless power supply directly into electric storage devices and DC power grids without novel equipment. The stored power is carries to loads through dc-ac converters. The DC generators could be controlled back to an unmoving speed as batteries tend to be stimulating to recover considerably more fuel.
Advantages of AC Generator -
These Generators are generally maintenance free, because of absence of brushes.
Easily step up and step down through transformers.
Transmission link size might be thinner because of step up feature
Size of the generator relatively smaller than DC machine
Losses are relatively less than DC machine
These Generator breakers are relatively smaller than DC breakers
Advantages of DC Generator - Mainly DC machines have the wide variety of operating characteristics which can be obtained by selection of the method of excitation of the field windings.
The output voltage can be smoothed by regularly arranging the coils around the armature .This leads to less fluctuations which is desirable for some steady state applications.
No shielding need for radiation so cable cost will be less as compared to AC
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When a current passes through a wire it produces a magnetic field. If you put this magnetic field in another magnetic field, it puts a force on the wire. This is known as the motor effect.
To determine the direction of the force you use a handy trick called Flemming's left hand rule. The way this works is by taking your left hand and making this shape with it. You then assign your first finger to the direction of the magnetic field, which is always north to south, your second finger to the direction of the current, and your thumb to the direction of the force.
For example, in this case, Flemming's left hand rule states that the force would act in this direction.
A simple electric motor works using this fact. It works by looping a coil of wire around to two electrical contacts inside a magnetic field. This causes one side of the wire to move up and the other part to move down, which causes the whole thing to spin. It is attached to something called a split ring commutator which is a clever way of swapping the contacts every half turn to keep it moving in the same direction. You can make the motor go faster by either increasing the current or by using a stronger magnetic field.
So next time you use your hair dryer, you’ll know something more about the way it spins.
2. CGP GCSE Physics AQA Revision Guide.
052 - Torque
In this video Paul Andersen begins by discriminating between translation and rotational motion. He then explains how a torque is the product of the lever arm and the force perpendicular. The lever arm must be perpendicular to the axis of rotation and the force must be perpendicular to the lever arm.
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Title: String Theory
Artist: Herman Jolly
All of the images are licensed under creative commons and public domain licensing:
“Balancing Act.” PhET. Accessed September 4, 2014. http://phet.colorado.edu/en/simulation/balancing-act.
MidnightLightning. English: SVG Version of Adjustable Wrench.jpg, April 14, 2009. Own work. http://commons.wikimedia.org/wiki/File:Adjustable_wrench2.svg.
Technik, RusCloud-SVG fileThe Lexikon der gesamten. English: SVG Variant of L-Door.png., September 14, 2010. Own work. http://commons.wikimedia.org/wiki/File:L-doorVector.svg.
This video is meant to explain the basics of torque and how to increase torque. Kinesiolgy is the study of Human body movement, which uses Torque.
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The abbreviation RMS stands for "root mean square." What do electrical engineers mean when they talk about that? You can learn more about this topic in any edition of "Teach Yourself Electricity and Electronics."
Are GMOs bad for your health? Or is this fear unfounded?
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#What is natural:
Genetic engineering for thousands of years:
# Are GMOs bad for your health
GMOs and gene flow:
Plants that are destined to be eaten are evaluated by different agencies
GMOs are safe– various studies and reports by respected authorities:
National Academies of Science, Engineering and Medicine:
An overview of the last 10 years of genetically engineered crop safety research:
Letter of 110 Nobel laureates vouching for GMOs:
# What good GMOs can do
# Look in the crystal ball:
plants that produce more nutrients:
Potential for landsparing:
# Further reading:
Bt cotton in India:
Article on popular science:
Blog series on GMOs:
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Are GMOs Good or Bad? Genetic Engineering & Our Food