Magnetism Electricity

Magnetism Electricity Most matter is electrically neutral; its atoms and molecules have the same number of electrons as protons. If a material somehow obtains extra electrons and attaches them to the atom's outer shells, that material has a negative (−) charge. Likewise, if a material loses electrons, it has an excess of positive (+) charges. The electric field from the excess of charges then causes the static electric effects of attraction, repulsion or a spark.

Magnetic fields are produced by the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. -> permanent magnets Magnetic fields are also produced by moving electric charges (current).

Magnetism Electricity An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work.

Magnetic fields are produced by the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. -> permanent magnets Magnetic fields are also produced by moving electric charges (current).

Magnetism Electricity Conductors (metals) Magnetic fields are produced by the intrinsic

magnetic moments of elementary particles associated with a fundamental quantum property, their spin. -> permanent magnets Magnetic fields are also produced by moving electric charges (current).

Insulators: material whose internal electric charges do not flow freely

Electromagnetism

Electromagnetic induction is the complementary phenomenon to electromagnetism. Instead of producing a magnetic field from electricity, we produce electricity from a magnetic field. Electromagnetism produces a steady magnetic field from a steady electric current but electromagnetic induction requires motion between the magnet and the coil to produce a voltage.

Connect the multimeter to the coil, and set it to the most sensitive DC voltage range. Move the magnet slowly to and from one end of the electromagnet, noting the polarity and magnitude of the induced voltage. Experiment with moving the magnet, and discover for yourself what factor(s) determine the amount of voltage induced. Try the other end of the coil and compare results. Try the other end of the permanent magnet.

Resistance The resistance (R) of an object is defined as the ratio of voltage across it (V) to current through it (I). Capacitance Capacitance is the ability of a body to store an electrical charge. Any object that can be electrically charged exhibits capacitance. A common form of energy storage device is a parallel-plate capacitor. If the charges on the plates are +q and −q, and V gives the voltage between the plates, then the capacitance C is Inductance Inductance is the property of a conductor by which a change in current in the conductor "induces" (creates) a voltage in both the conductor itself (self-inductance) and in any nearby conductors (mutual inductance).

a voltage is induced across an inductor, equal to the product of the inductor's inductance, and current's rate of change through the inductor.

Motor (armature) rotation is caused by the simultaneous attraction and repulsion between the electromagnetic

field in the armature and a fixed magnetic field

Fixed Magnets

Armature

Induced Magnetic Field (Due to current)

Fixed Magnetic Field

Force

A Conductor in a Fixed Magnetic Field

A Current Carrying Conductor in a Fixed Magnetic Field

N S

A Motor Armature in a Fixed Magnetic Field

The magnetic field surrounding a current carrying conductor interacts with an

existing magnetic field.

Direction of Force (Torque) acting to turn the Armature (Conductor)

http://www.taringa.net/posts/offtopic/16947327/Gifs-que-explican-como-funcionan-las-cosas.html

The Armature of a Brush Commutated DC Motor is made up of Current Carrying

Conductors Wrapped Around an Iron Core

The Motor Armature is an electro Magnet and Operates according to the Principles Described in

this Slide Show

Vacuum Tubes

Vacuum Tubes

Vacuum Tubes

Semiconductors • Semiconductors are materials that conduct weakly. • Insulators in some conditions and as conductors in others. • Semiconductors can be doped; this is when another substance is

added to the semiconductor to change its properties. • Donor dopants produce an excess of electrons -> n-type. • Acceptor dopants produce an excess of positive “holes” where

there are no electrons -> p-type.

Diodes • A diode is a circuit element which essentially is a resistor with

polarity; it has a different resistance in one direction than in the other. • Most diodes have no resistance in one direction and very high

resistance in the other, so that they only allow current to flow in one direction.

• For semiconductor diodes, the diode behaves as an insulator until a certain voltage is achieved across the diode. It then behaves as a conductor, allowing current to pass. When this happens, the diode is forward-biased.

Transistors • Semiconductor transistors: current through them is controlled • the Bipolar Junction Transistor (BJT). • In the NPN BJT, a layer of p-type semiconductor separates two

sections of n-type semiconductor. When there is a voltage across the two n-type layers, no current can pass through. When positive voltage is applied to the p-type layer, however, the transistor becomes conductive, and current can pass through.

• The terminal that receives current is called the collector. • The terminal that releases current is called the emitter. • The terminal that controls whether the transistor is ‘on’ is called

the base.