Presentation on theme: "Rubbing a plastic leader with structure produces a new force of attraction between the ruler and bits the paper. As soon as the ruler is brought close come bits of paper,"— Presentation transcript:

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2 Rubbing a plastic leader with structure produces a brand-new force that attraction in between the ruler and bits of paper. As soon as the leader is lugged close come bits the paper, the attractive electric force increases the document bits upward against the force of gravity. This force is stronger than gravity because it can pull UP versus it!

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3 There are various other differences in between this “new” force and also gravity: Paper is attractive to a plastic ruler just after the ruler has been rubbed; if friend wait a while, the attractive property of the ruler disappears. Gravity, ~ above the other hand, does no require any type of “action” and also does no disappear. The ancient Greeks noticed effects similar to that of the ruler once they rubbed amber with fur. The Greek word for amber is elektron, and today this attractive home is dubbed electric. Things that exhibits electrical interaction after ~ rubbing is stated to be charged.

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4 A Microscopic see of ChargeElectric dues exist within atoms. In 1897, J.J. Thomson uncovered that all products contain light, negatively fee particles the he referred to as electrons. In between 1909 and also 1911, Ernest Rutherford, a student of Thomson from brand-new Zealand, uncovered that the atom has actually a massive, positively charged nucleus. (Rutherford’s Experiment) when the confident charge of the nucleus equals the an adverse charge the the neighboring electrons, then the atom is neutral.

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5 as soon as wool is offered to fee a rubber rod, electrons are eliminated from the wool atoms and also cling come the rubber atoms. In this way, both objects come to be charged (the rod an adverse because it has extra electrons; the wool POSITIVE because there space not sufficient electrons left come balance the proton in the nucleus)

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6 Conductors and also InsulatorsHold a plastic rod or comb at its midpoint and also rub only one end. Friend will find that only the rubbed end becomes charged. In other words, the charges that you moved to the plastic stayed where they were put; lock did no move. A product through which a charge will certainly not move conveniently is referred to as an electric insulator. Glass, dried wood, most plastics, cloth, and also dry air are all good insulators. Moist (high humidity) wait is no as great an insulator.

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7 Even mice deserve to conduct electricityA material that enables charges to move around easily is called an electrical conductor. Electron carry, or conduct, electrical charge v the metal. Metals are great conductors since at least one electron on every atom that the metal deserve to be eliminated easily. This electrons act as if castle no much longer belong to any kind of one atom, but to the metal as a whole; consequently, lock move openly throughout the piece of metal. Also mice deserve to conduct electricity

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8 Charges placed on a conductor will spread over the whole surface (a)Charges put on a conductor will spread over the entire surface (a). Charges placed on an insulator will continue to be where castle are put (b).

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9 There are two type of electrical charges: positive and also negative.Charges exert pressures on other charges at a distance. The pressure decreases promptly with increasing distance. The pressure is stronger as soon as the charges space closer together. Favor charges repel; opposite charges attract.

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10 Attract (opposite charge!)A charged rod, when carried close to another charged and also suspended rod, will tempt or loss the suspended rod. Defeat (same charge!) repel (same charge!) attract (opposite charge!)

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11 Charging by conductionWhen a negatively fee rod is touched to the knob of an electroscope, electrons are added to the knob. These charges spread out over all the metal surfaces. As shown, the 2 leaves are charged negatively and repel every other; therefore, they spread apart. The electroscope has been given a network charge. Charging a neutral human body by poignant it v a charged human body is called charging by conduction.

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12 A negatively fee electroscope will have actually its leaves spread apart (a). A negatively fee rod pushes electrons down to the leaves, causing them to spread farther apart (b). A positively fee rod attracts some of the electrons, resulting in the pipeline to spread apart much less (c).

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13 Does no touch! Charging by induction expect that 2 identical, insulated steel spheres space touching. As soon as a negatively charged rod is lugged close to one, as in, electrons from the first sphere will certainly be required onto the ball farther from the rod and will do it negative charged. The closer round is now positively charged. If the spheres are separated while the pole is nearby, each ball will have actually a charge, and the charges will certainly be equal however opposite, together shown. This process of charging an item without emotional it is called charging by induction.

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14 Coulomb provided a similar type of device to measure up the force between two “pith balls”. The measured the speak or twist created by the attractive and repulsive forces.

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15 Coulomb’s Law: force depends on DistanceCoulomb uncovered how the force between the 2 charged spheres depended on the distance. He verified that the force, F, varied inversely through the square the the distance in between the centers that the spheres.

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16 Force depends on ChargeTo inspection the method in i beg your pardon the force depended on the quantity of charge, Coulomb had to readjust the fees on the spheres in a measure way. He uncovered that the force varied straight with the charge of the bodies.

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17 after ~ many comparable measurements, Coulomb summarized the outcomes in a law now well-known as Coulomb’s law: the size of the force between charge qA and also charge qB, be separated by a street r (sometimes d!) , is proportional come the magnitude of the charges and also inversely proportional to the square the the distance in between them. Coulomb’s law

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18 One Coulomb is the charge of 6. 24X 1018 electron or protonsOne Coulomb is the fee of 6.24X 1018 electron or protons. A typical lightning bolt can lug 5 C to 25 C the charge. The charge on a solitary electron is 1.60X C. The size of the charge of one electron is called the elementary school charge. Even tiny pieces that matter, such as coins, contain up to 106 C of an adverse charge. This massive amount of negative charge produces practically no outside effects since it is balanced by an equal amount of optimistic charge (in the nucleus).

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19 Attract….. Or Repel??

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20 Charles-Augustin de Coulomb b. June 14, 1736, Angoulme, France d. AugCharles-Augustin de Coulomb b. June 14, 1736, Angoulme, France d. Aug.


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23, 1806, Paris

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21 Need to look increase “fundamental charge” the electron - 1.60X 10-19 C Let’s try a problem… 2 electrons in an atom are separated by X m, the usual size of one atom. What is the electric force in between them? need to look up “fundamental charge” the electron X C Coulomb’s Law constant (K) : x 109 N•m2/C2

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