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Angular momentum The quantity of the rotational motion, which is identical to mass (m) in the linear motion, is the moment of inertia (I). The quantity of the rotational motion, which is identical to the velocity (v) in the linear motion, is the angular velocity (ω). Thus, the rotating object has angular momentum that can … Read more
Review a rotating particle. The particle with mass m is given the force F so that the particle rotates about the axis O. The particle is r apart from the axis of rotation. First, the particle is in rest (v = 0). After moved by the force of F, the particles move with a certain speed so that the particles have tangential acceleration. The relationship between force (F), mass (m), and the tangential acceleration of particles are expressed by equation 3:
In a conductor such as copper, there are electrons that move randomly at high speed freely but not escape from the metal. Electrons that can move freely are called free electrons. Although the electrons move freely in all directions, there is no total flow of electrons in a particular direction. This condition occurs when there is no potential difference between the two ends of the copper wire.
When the wire is connected to an electrical source, a potential difference arises between the two ends of the copper wire, so that an electric field appears within the copper wire. The existence of an electric field causes free electrons to experience the electric force F = q E = e E, where F = electric force, e = electron charge, E = electric field. This electric force causes all the electrons that are moving freely to accelerate together, which is the same direction as the electric force.
The definition of capacitor is a device that stores electrical charge and electrical potential energy. The simple capacitor consists of two-conductor plates or sheets that are placed close together but do not touch each other and are separated by an insulator or a vacuum. Conductors are materials that can conduct electric current such as metals, while insulators are materials that cannot conduct electric current such as plastic.
At first, the two conductors are not electrically charged or electrically neutral. In order for one conductor to be positively charged and the other conductor to be negatively charged, then there must be a transfer of electrons from one conductor to another. The electrons are on the surface of the atom, so they are easy to move. After the electron has moved from one conductor to another, one of the conductors has an excess of electrons (lack of protons)
so that it becomes negatively charged, while the other conductor has an electron deficiency (excess proton) so that it becomes positively charged. A detailed description of the process of charging electric charges on capacitors is reviewed on the topic of storing electrical energy in capacitors.
Electric potential is defined as the electric potential energy per unit charge. Suppose that when it is at point a, the charge q has the electric potential energy equal to EPa, then the electric potential at point a is formulated as follows:
V = electric potential, EP = electric potential energy, q = electric charge
V is not only at point a but also at all points in the electric field. Point a is used as an example. As will be explained later, the V does not depend on the charge q.
Before studying this topic, first understand work, the conservative forces, the relationship between the conservative forces with potential energy, the electric forces and the electric field.
In addition to the gravitational force and spring force, the other example of the conservative force is the electric force. To better understand why the electric force is called the conservative force, understand the following explanation.
Electric field by a single point charge
To calculate the electric field produced by a single positive charge, the first step is to select the spherical Gauss surface with radius r where the center of the sphere is at the single charge. The surface area of the ball is 4πr2.
The electric field coming out of the center of the sphere penetrates perpendicular to the surface of the sphere so that the formula of electric flux is Φ = E A. The formula of the Gauss’s law is Φ = Q/εo
Regarding Coulomb’s law, the force between electric charges has been studied. In a review of the electric field, another form of Coulomb’s law has been discussed, which is expressed by the equation F = q E,
where F is the electric force, q is the electric charge and E is the electric field. It can be said that Coulomb’s law is a law of physics that explains the relationship between the electric charge (q) and the electric field (E).
Gauss’s law is another physics law that explains the relationship between the electric charges and the electric fields. Gauss’s law was formulated by Carl Friedrich Gauss (1777-1855), a German theoretical physicist and mathematician.
Regarding the electric field, has been discussed the definition and equation of the electric field which can be used to calculate the electric field strength produced by an electric charge, some electric charge or by an electric charge distribution. The calculation of the electric field strength produced by an electric charge or two electric charges is easily solved using the formula of electric field strength. If what is calculated is the electric field strength generated by an electric charge distribution, the calculation is more complicated if the formula for electric field strength is used, but it is easier to use Gauss’s law. Before studying Gauss law in depth, first understood that electric flux because of the concept of electric flux used in Gauss law.
On the subject of the electric charge, it was learned that like charges repel each other, while unlike charges attract each other. If a positively charged object is brought close to a negatively charged object, the two objects pull together so that they move toward each other. Conversely, if a positively charged object is brought close to a positively charged object, then the two objects repel each other so that they move away from each other. As studied on the subject of Coulomb’s law, electrically charged objects can accelerate other electrically charged objects because there is an electrical force acting between these electrically charged objects. The electric force that is exerted by an electrically charged object on other electrically charged objects is one example of a force that can act without contact. Another example of the force that can act at a distance is the force of gravity. The gravitational force is exerted by a mass object on the other mass objects.
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