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2024年4月29日 · Electric power is characterized by current or the flow of electric charge and voltage or the potential of charge to deliver energy. A given value of power can be produced by any combination of current and voltage values. If the current is direct, electronic charge progresses always in the same direction through the device receiving power.
- The Editors of Encyclopaedia Britannica
- Overview
- Electrostatics
- Coulomb’s law
electricity, phenomenon associated with stationary or moving electric charges. Electric charge is a fundamental property of matter and is borne by elementary particles. In electricity the particle involved is the electron, which carries a charge designated, by convention, as negative. Thus, the various manifestations of electricity are the result o...
Electrostatics is the study of electromagnetic phenomena that occur when there are no moving charges—i.e., after a static equilibrium has been established. Charges reach their equilibrium positions rapidly because the electric force is extremely strong. The mathematical methods of electrostatics make it possible to calculate the distributions of th...
Static electricity is a familiar electric phenomenon in which charged particles are transferred from one body to another. For example, if two objects are rubbed together, especially if the objects are insulators and the surrounding air is dry, the objects acquire equal and opposite charges and an attractive force develops between them. The object that loses electrons becomes positively charged, and the other becomes negatively charged. The force is simply the attraction between charges of opposite sign. The properties of this force were described above; they are incorporated in the mathematical relationship known as Coulomb’s law. The electric force on a charge Q1 under these conditions, due to a charge Q2 at a distance r, is given by Coulomb’s law,
The bold characters in the equation indicate the vector nature of the force, and the unit vector r̂ is a vector that has a size of one and that points from charge Q2 to charge Q1. The proportionality constant k equals 10−7c2, where c is the speed of light in a vacuum; k has the numerical value of 8.99 × 109 newtons-square metre per coulomb squared (Nm2/C2). Figure 1 shows the force on Q1 due to Q2. A numerical example will help to illustrate this force. Both Q1 and Q2 are chosen arbitrarily to be positive charges, each with a magnitude of 10−6 coulomb. The charge Q1 is located at coordinates x, y, z with values of 0.03, 0, 0, respectively, while Q2 has coordinates 0, 0.04, 0. All coordinates are given in metres. Thus, the distance between Q1 and Q2 is 0.05 metre.
Britannica Quiz
Electricity: Short Circuits & Direct Currents
The magnitude of the force F on charge Q1 as calculated using equation (1) is 3.6 newtons; its direction is shown in Figure 1. The force on Q2 due to Q1 is −F, which also has a magnitude of 3.6 newtons; its direction, however, is opposite to that of F. The force F can be expressed in terms of its components along the x and y axes, since the force vector lies in the xy plane. This is done with elementary trigonometry from the geometry of Figure 1, and the results are shown in Figure 2. Thus,in newtons. Coulomb’s law describes mathematically the properties of the electric force between charges at rest. If the charges have opposite signs, the force would be attractive; the attraction would be indicated in equation (1) by the negative coefficient of the unit vector r̂. Thus, the electric force on Q1 would have a direction opposite to the unit vector r̂ and would point from Q1 to Q2. In Cartesian coordinates, this would result in a change of the signs of both the x and y components of the force in equation (2).
How can this electric force on Q1 be understood? Fundamentally, the force is due to the presence of an electric field at the position of Q1. The field is caused by the second charge Q2 and has a magnitude proportional to the size of Q2. In interacting with this field, the first charge some distance away is either attracted to or repelled from the second charge, depending on the sign of the first charge.
2024年4月25日 · static electricity, form of electricity resulting from the imbalance between positive and negative charges within a material that occurs when electrons (the negatively charged particles in an atom) move from one material to another.
2024年5月3日 · electric field. Related Topics: electricity. field. built-in electric field. electric wind. electric field strength. On the Web: Pressbooks Create - Introduction to Physics - Electric Field (May 03, 2024) electric field, an electric property associated with each point in space when charge is present in any form.
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2024年4月2日 · charge carrier. point charge. electric charge, basic property of matter carried by some elementary particles that governs how the particles are affected by an electric or magnetic field. Electric charge, which can be positive or negative, occurs in discrete natural units and is neither created nor destroyed.
2024年3月28日 · An electric circuit includes a device that gives energy to the charged particles constituting the current, such as a battery or a generator; devices that use current, such as lamps, electric motors, or computers; and the connecting wires or transmission lines.
What is energy? What is the unit of measurement for energy? Can energy be created? energy, in physics, the capacity for doing work. It may exist in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. There are, moreover, heat and work—i.e., energy in the process of transfer from one body to another.
