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PT UNIT 1 Subunit 3

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.

Two kinds of charges Positive and Negative Charges cause electrical force

Law of Charges: Like charges repel and unlike charges attract.

the origin of electrical charge is the atom
the origin of electrical charge is the atom. All matter is made of atoms. In the center of the atom is a nucleus that contains positive charged protons.

The charge of a normal atom is zero.
Charges can be transferred from one object to another by adding electrons. A neutral atom has a zero charge. Adding electrons to a neutral object makes a negative charge object. Taking away electrons from a neutral object makes a positive charged object.

Principle of conservation of charge: The net charge in an isolated system never changes.

Coulomb’s Law

Elementary Charge is the charge of one electron or one proton.

A mass as potential if it is moved through a gravitational field.

A charge has potential if it is moved through an electric field
A charge has potential if it is moved through an electric field. The field creates an electrical potential between A and B.

Electrical forces create a voltage difference whenever the positive and negative charge are separated.

Voltage act like a force in an electrical system
Voltage act like a force in an electrical system. It causes electrons to move. Electrons are negative charged particles found in the outer part of the atom.

Voltage is the forcelike quantity in electrical systems.
Voltage is measured in volts.

A flow of charge is called a current.

Electric systems are made of (1)Voltage source) (2) conductors (3) Control elements (4) load
Voltages source-Battery, electrical plug in, generator Conductors-wires Control element- switch Load-appliances, lights, etc

Electrical circuit is a closed path made by connecting voltage sources, control elements and loads.

Two types of electricity.
Direct current (DC) is current that moves in one direction only. Alternating current (AC) is current that moves back and forth in the wire. Current is movement of electrons.

Dry cell batteries uses a paste material that contains the chemical that produces the voltage.
Wet cell batteries use a liquid material that contains the chemical to produce the voltage.

Primary cells are those cells that cannot be recharged.
Secondary cells are those cells that can be recharged.

The terminals of a battery are called electrodes.
The positive electrode is called the Anode. The negative electrode is called the cathode.

Connecting voltage sources in series so they add together requires that the positive electrode from one source is connected to the negative electrode of the other source.

Main sources of AC are generators and electrical outlets.
The rate at which the current is changing back and forth is its frequency (f) Units are cycles/sec = hertz

Voltage difference can be created by
(1) Chemical means –Chemical energy in dry or wet cells separates the charges to form a positive pole and a negative pole. (2) Magnetic/Mechanical– A coil of wire moving in a magnetic field produces a force on electrical charges that separates the positive and negative charges. (3) Light- light energy that falls on certain materials causes the separation of electrons from their atoms.

Voltage is measured by using a volt meter, panel meter and a oscilloscope and a multimeter.