Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Nuclear physics wikipedia , lookup
Electromagnetism wikipedia , lookup
Fundamental interaction wikipedia , lookup
History of electromagnetic theory wikipedia , lookup
Anti-gravity wikipedia , lookup
History of the battery wikipedia , lookup
Electrical resistivity and conductivity wikipedia , lookup
Lorentz force wikipedia , lookup
Electrical resistance and conductance wikipedia , lookup
Atomic nucleus wikipedia , lookup
Chapter 1.3 Notes Voltage • Two universal forces in nature are Gravitational Force and Electrical Force. • They are universal because each force acts the same everywhere in the universe. • Gravitational Forces act between two or more masses. • Electrical Forces act between two or more charges. • Newton’s Universal Law of Gravitation: every object in the universe attracts every other object with a force that (for two bodies) is directly proportional to the mass of each body and that is inversely proportional to the square of the distance between them. • The gravitational force Fg is exerted equally on both masses but the direction of the force is different for both masses. • The gravitational force is always an attractive force. • The property of an object that causes electrical force is called charge. • There are two types of charges; positive and negative. • Two objects with the same charge, both positive or both negative, repel each other. • Two objects with opposite charges attract each other. • The origin of electric charge is found in the atom. • The nucleus of an atom contains most of the mass, in the neutrons and protons. • Neutrons have no charge and so they are neutral. • Protons have a positive charge. • The nucleus is surrounded by a cloud of electrons. • Electrons have a negative charge. • The charge of the electron is equal to the charge of the proton. • The force of attraction between the proton and electron is what keeps the electron bound to the nucleus. • A normal atom has no charge, since it has an equal amount of electrons and protons. • You can transfer charge from one object to another because the outermost electrons in the atoms of some substances are not tightly bound to the nucleus and can be removed. • The net electrical charge in a system never changes; Principle of conservation of charge. • Coulomb’s Law : the electrical force between two charged bodies is proportional to the charge on each body and inversely proportional to the square of the distance between them. • The charge on one electron or proton is 1.6 x 10 -19 ; This is called the Elementary Charge. • A field is an imaginary construction used by scientists to help them understand and predict how forces are transmitted from one object to another. • The direction of a field is shown with arrows. • Where the lines are close together, the magnitude of the field is high. • Where the lines are far apart, the magnitude of the field is low. • Field lines can only be shown in two dimensions, but true electric fields are 3 Dimensional. • If you move a charge against an electric field, you must exert a force on the charge. • The charge possesses a potential because if it is released, the charge will accelerate towards its original position; the field creates an electric potential difference. • In a uniform electric field of magnitude E, the electrical potential difference VAB between the points A and B, separated by a distance of d is the following: VAB = E x d • The unit of measurement for electric potential difference is the Volt. • Electric potential difference is sometimes simply called voltage. • Voltage is the main mover in electrical systems, like pressure is the main mover in fluid systems. • A flow of charge is called an electrical current. • In the electrical system, current can be maintained with a battery. • Electrical systems contain four major components: • Voltage Source – battery • Conductor – wire • Load – light bulb • Control Element - switch The load in an electrical system is usually an appliance or machine such as an electric motor. • An electrical conductor is a material through which charge can easily flow. •The control element can be a switch that turns the current on or off. • An electrical circuit is a closed path for current to flow created by connecting voltage sources, conductors, control elements, and loads. • There are two types of current: Direct and Alternating Current. • In direct current (DC), the electric charge flows in one direction. • In alternating current (AC), the electric charge flows back and forth. • Batteries produce direct current and alternators produce alternating current. • Another word for a battery is a cell. • A cell is a single unit that contains chemicals. • As the chemicals react, electrons are removed from certain molecules, leaving behind positively charged ions. • The electrons and ions are separated and this charge separation creates a voltage. • Primary cells are batteries designed for one time use. • Secondary cells are batteries that can be recharged. • In a rechargeable battery, current is sent through the battery in a reverse direction, which reverses the direction of the chemical reaction and makes the material available again to produce voltage. • The voltage output of a battery is measured between two terminals. • These terminals are called electrodes. • One electrode is positive and the other is negative. • When connected in a circuit, electrons flow through the circuit from the negative to the positive. • The negative electrode is called a cathode. • The positive electrode is called the anode. • Batteries can be added together in series to produce a higher voltage. • Adding cells in series means that the positive terminal from one cell is connected to the negative terminal of another battery. • In a series circuit, there is only one path for current. • In a parallel circuit, there are many paths for the current to flow. Shorthand symbols: • Battery – • Light bulb – • Switch – • Conductors – Schematic of a simple circuit: • An AC voltage source reverses the positive and negative terminals many times per second. A majority of AC circuits cycle at a rate of 60 times per second. The cycling rate is called the frequency. • Frequency is measured in cycles per second, or hertz.