positively charge ions result from the loss of electrons and are called cations.
Negatively charge ions result from the gain of electrons and are called anions.
The charge on an ion is called an electrostatic charge .
An object becomes electrostatically charged by
Friction ,which transfers electrons between two objects in contact,
Contact with a charged body which results in the transfer of electrons,
Induction which produces a charge redistribution of electrons in a material.
Arbitrary numbers of protons (+) and electrons (-) on a comb and in hair (A) before and (B) after combing. Combing transfers electrons from the hair to the comb by friction, resulting in a negative charge on the comb and a positive charge on the hair.
An electrical charge has an electrical field that surrounds it.
In order to move a second charge through this field work must be done .
Bringing a like charge particle into this field will require work since like charges repel each other and bringing an opposite charged particle into the field will require work to keep the charges separated.
In both of these cases the electrical potential is changed.
Electric current means the flow of charges which is analogous to water flow
It is the charge that flows , and the current is defined as the flow of the charge .
An electrical circuit contains some device that acts as a source of energy as it gives charges a higher potential against an electrical field.
The charges do work as they flow through the circuit to a lower potential.
The charges flow through connecting wires to make a continuous path.
A switch is a means of interrupting or completing the circuit.
The source of the electrical potential is the voltage source .
A simple electric circuit has a voltage source (such as a generator or battery) that maintains the electrical potential, some device (such as a lamp or motor ) where work is done by the potential, and continuous pathways for the current to flow.
Voltage is a measure of the potential difference between two places in a circuit.
Voltage is measured in joules/coloumb .
The rate at which an electrical current ( I ) flows is the charge ( q ) that moves through a cross section of a conductor in a give unit of time ( t ),
I = q/t.
the units of current are coulombs/second.
A coulomb/second is an ampere ( amp ).
What is the nature of the electric current carried by these conducting lines? It is an electric field that moves at near the speed of light. The field causes a net motion of electrons that constitutes a flow of charge, a current .
(A) A metal conductor without a current has immovable positive ions surrounded by a swarm of randomly moving electrons. (B) An electric field causes the electrons to shift positions, creating a separation charge as the electrons move with a zigzag motion from collisions with stationary positive ions and other electrons.
Resistors can be connected in series; that is, the current flows through them one after another. The circuit here shows three resistors connected in series, and the direction of current is indicated by the arrow.
Resistors can be connected such that they branch out from a single point (known as a node), and join up again somewhere else in the circuit. This is known as a parallel connection. Each of the three resistors in the figure below is another path for current to travel between points A and B.
The Earth’s magnetic field is thought to originate with moving charges.
The core is probably composed of iron and nickel, which flows as the Earth rotates, creating electrical currents that result in the Earth’s magnetic field.
The earth's magnetic field. Note that the magnetic north pole and the geographic North Pole are not in the same place. Note also that the magnetic north pole acts as if the south pole of a huge bar magnet were inside the earth. You know that it must be a magnetic south pole since the north end of a magnetic compass is attracted to it and opposite poles attract.
A bar magnet cut into halves always makes new, complete magnets with both a north and a south pole. The poles always come in pairs. You can not separate a pair into single poles.
Oersted discovered that a compass needle below a wire (A) pointed north when there was not a current , (B) moved at right angles when a current flowed one way, and (C) moved at right angles in the opposite direction when the current was reversed .
(A) In a piece of iron, the magnetic domains have random arrangement that cancels any overall magnetic effect (not magnetic). (B) When an external magnetic field is applied to the iron, the magnetic domains are realigned, and those parallel to the field grow in size at the expense of the other domains, and the iron becomes magnetized .
A magnetic compass shows the presence and direction of the magnetic field around a straight length of current-carrying wire.
When a current is run through a cylindrical coil of wire, a solenoid , it produces a magnetic field like the magnetic field of a bar magnet. The solenoid is known as electromagnet .
The strength of the magnetic field produced by an electromagnet is proportional to the electric current in the electromagnet.
A galvanometer measures electrical current by measuring the magnetic field.
A galvanometer can measure current, potential difference, and resistance.
A galvanometer measures the direction and relative strength of an electric current from the magnetic field it produces . A coil of wire wrapped around an iron core becomes an electromagnet that rotates in the field of a permanent magnet. The rotation moves pointer on a scale.