Un televisor es un aparato electrónico destinado a la recepción y reproducción de señales de televisión. Usualmente consta de una pantalla y mandos o controles. La palabra viene del griego tele (τῆλε; lejos) y latín vis (ver).
Su funcionamiento se fundamenta en el fenómeno de la fotoelectricidad, que es el responsable de la transformación de la luz en corriente eléctrica en una cámara que se puede trasmitir por ondas de alta frecuencia hasta las antenas de recepción y se reproduce en la pantalla de nuestros televisores. El televisor es uno de los aparatos de más uso cotidiano.
ResoluciónLa Resolución en píxeles es la cantidad de puntos individuales llamados píxeles en una pantalla dada. Una resolución típica de 720x480 significa que la pantalla del televisor tiene 720 píxeles horizontales y 480 píxeles en el eje vertical, la resolución afecta la nitidez de la imagen, Cuanto mayor la resolución de una pantalla, mayor es su nitidez. La primera resolución tenía 48 líneas y cada una de las fábricas usaba sistemas diferentes. La estandarización de estos sistemas comienza en julio de 1941 cuando se logró el sistema NTSC, válido para todos los estados de Estados Unidos, de 325 líneas. Europa logró un sistema de 625 líneas al término de la guerra, Francia poseía uno propio de 819 líneas e Inglaterra mantuvo el suyo de 405 líneas. Posteriormente el sistema NTSC fue mejorado
miércoles, 28 de octubre de 2009
Resístanse:
Nichrome resists more the current tan copper. Nichrome has a bigger resistance than copper.
Every material has an electrical resistance. The greater the material´s resistance, the smaller is the current which through it.
Conductors like copper and aluminum have very low resistances. They carry large currents well but insulators have very large resistances. They only allow small currents to flow through them.
When the current flows through a wire, electrical energy is changed to heat energy.
When a current is pushed through a high resistance wire by a large voltage large amounts of heat are produced
Nichrome resists more the current tan copper. Nichrome has a bigger resistance than copper.
Every material has an electrical resistance. The greater the material´s resistance, the smaller is the current which through it.
Conductors like copper and aluminum have very low resistances. They carry large currents well but insulators have very large resistances. They only allow small currents to flow through them.
When the current flows through a wire, electrical energy is changed to heat energy.
When a current is pushed through a high resistance wire by a large voltage large amounts of heat are produced
Portable power packs.
If you are going to be absolutely correct, you should call a torch battery a dry cell. Is called dry because it has no liquid in it a battery is made up from a collection of cells joined together. A 9v. Transistor radio battery contains small calls joined in series a 12v. Car battery contains six 2v. Lead-acid cells joined in series.
There are many different cells in use today. Here six of them, with their advantages and disadvantages.
The dry cell:
Is the most commonly used cells. It is often used intorches.It is cheap, easily carried and has no liquid to spill.
The mercury cell:
Can be made into small ´´button cells´´. Even very small mercury cells can produce large currents for a short time or small currents for a long time.
The lead-acid cell:
Can produce large currents. A battery of lead-acid cells can produce the large current needed to start a car. The cell can be recharged when flat. It is heavy and contains acid which can spill.
The reserve cell:
Does not work until salt water is added. Then it can give a high current for a short time or a small current for a long time.
The lithium cell:
Is small and light. It is very reliable and long lasting. Lithium cells are expensive.
The nickel-cadmium cell:
Is the rechargeable battery sold in the shops? It is light and is completely sealed. It cannot give very large currents and is expensive.
Questions.
1 What is a battery?-Is a dry cell.
How a car battery is made up?-it´s made up from a collection of cells joined together.
2Heaning acids only use small currents. Suggest two reasons why a mercury cell is a good cell for running a hearing acid.
Because it has a long current and a short current.
3. A) suggest reasons why the dry cell is the most commonly used cell.
-It is cheap, easily carried and has no liquid to spill
b) If you leave a torch on, the bulb gradually gets glimmer. Why?
4 One of the six cells can be found in a life raft. Which cell is this? The reserve cell:
Does not work until salt water is added.
Why might it be used for?
Then it can give a high current for a short time or a small current for a long time.
Why might it be used for?
5try to find out: What heart Pacemakers are. Then suggest why lithium cells are used to power them?
Un marcapasos cardíaco es un aparato pequeño que ayuda a que su corazón lata más uniformemente. Una células especiales dentro del corazón emiten impulsos eléctricos a los músculos del corazón para que este lata. Estas células se denominan células marcapasos. Si algo previene que las células marcapasos ejecuten su función, su corazón no puede latir normalmente. Los médicos pueden colocar un marcapasos artificial compuesto de electrodos (alambres delgados flexibles) y un generador (baterías).
If you are going to be absolutely correct, you should call a torch battery a dry cell. Is called dry because it has no liquid in it a battery is made up from a collection of cells joined together. A 9v. Transistor radio battery contains small calls joined in series a 12v. Car battery contains six 2v. Lead-acid cells joined in series.
There are many different cells in use today. Here six of them, with their advantages and disadvantages.
The dry cell:
Is the most commonly used cells. It is often used intorches.It is cheap, easily carried and has no liquid to spill.
The mercury cell:
Can be made into small ´´button cells´´. Even very small mercury cells can produce large currents for a short time or small currents for a long time.
The lead-acid cell:
Can produce large currents. A battery of lead-acid cells can produce the large current needed to start a car. The cell can be recharged when flat. It is heavy and contains acid which can spill.
The reserve cell:
Does not work until salt water is added. Then it can give a high current for a short time or a small current for a long time.
The lithium cell:
Is small and light. It is very reliable and long lasting. Lithium cells are expensive.
The nickel-cadmium cell:
Is the rechargeable battery sold in the shops? It is light and is completely sealed. It cannot give very large currents and is expensive.
Questions.
1 What is a battery?-Is a dry cell.
How a car battery is made up?-it´s made up from a collection of cells joined together.
2Heaning acids only use small currents. Suggest two reasons why a mercury cell is a good cell for running a hearing acid.
Because it has a long current and a short current.
3. A) suggest reasons why the dry cell is the most commonly used cell.
-It is cheap, easily carried and has no liquid to spill
b) If you leave a torch on, the bulb gradually gets glimmer. Why?
4 One of the six cells can be found in a life raft. Which cell is this? The reserve cell:
Does not work until salt water is added.
Why might it be used for?
Then it can give a high current for a short time or a small current for a long time.
Why might it be used for?
5try to find out: What heart Pacemakers are. Then suggest why lithium cells are used to power them?
Un marcapasos cardíaco es un aparato pequeño que ayuda a que su corazón lata más uniformemente. Una células especiales dentro del corazón emiten impulsos eléctricos a los músculos del corazón para que este lata. Estas células se denominan células marcapasos. Si algo previene que las células marcapasos ejecuten su función, su corazón no puede latir normalmente. Los médicos pueden colocar un marcapasos artificial compuesto de electrodos (alambres delgados flexibles) y un generador (baterías).
moving charges.
U can do some hair rising experiments with a van de Graff generator. This is a machine for building up and storing electric charge, when it´s switched on, negative charge collected on the dump. The dump becomes negatively charge.
STORING CHARGE:
If u stands on a piece of plastic and touches the dump your body collects extra negative charge from the dump. That´s when your hair stands on end. Each hair becomes negatively charge the hairs repeal each other.
LOSING CHARGE:
If u then touch water tap your body loses this charge. Your hair goes back to normal. The charges flow from your body alone the water pipe to the air. You can feel them go, your fingers tingle.
FLOW OF CHARGE:
There are two good wishes of showing this flow of charge. You can connect a neon bull between the generator and the water tap. The bull glows as the charges flow fluid. You can also connect in a meter which meters small electric currents. The flow of charge through the meter makes the meter needle move
STORING CHARGE:
If u stands on a piece of plastic and touches the dump your body collects extra negative charge from the dump. That´s when your hair stands on end. Each hair becomes negatively charge the hairs repeal each other.
LOSING CHARGE:
If u then touch water tap your body loses this charge. Your hair goes back to normal. The charges flow from your body alone the water pipe to the air. You can feel them go, your fingers tingle.
FLOW OF CHARGE:
There are two good wishes of showing this flow of charge. You can connect a neon bull between the generator and the water tap. The bull glows as the charges flow fluid. You can also connect in a meter which meters small electric currents. The flow of charge through the meter makes the meter needle move
Electric sparks:
1: why do clouds become charged? Because they contains tiny crystals of ice which are constantly moving and rubbing on each other.
2- What is a flash of lightning? When is a lightning produced? Is an avalanche of electrons?
It´s produced when a thundercloud can become so highly charged that huge numbers of electrons jump the gap between a cloud and earth.
3- What special precautions are taken in factories using flammable materials? Why are these precautions taken? The workers have to wear special shoes and clothes which don´t build up charges. Because even the smallest spark can produce an explosion.
4- Have you ever produced sparks? If so, explain what happened. Yes I did, when I was near to the TV and it give me a little bit of charge and then I touch another person because we have different charges so it produces a little sparks.
5- Airplanes become charged up when they fly through clouds. Explain why.
´cause they have to cross the clouds so the airplane takes the charge of the clouds and they don´t have any form to throw the energy to the earth, so when it arrive it throw the energy to the earth.
6- What causes a clap of thunder? The energy of the clouds and the energy of the earth found each other and when it happened it produce sound.
- Why tall buildings have lightning conductors?
- Cause is more probable that a spark fall in the tall buildings so they need a conductor to can throw all the energy that can fall in the building and throw it to the earth
1: why do clouds become charged? Because they contains tiny crystals of ice which are constantly moving and rubbing on each other.
2- What is a flash of lightning? When is a lightning produced? Is an avalanche of electrons?
It´s produced when a thundercloud can become so highly charged that huge numbers of electrons jump the gap between a cloud and earth.
3- What special precautions are taken in factories using flammable materials? Why are these precautions taken? The workers have to wear special shoes and clothes which don´t build up charges. Because even the smallest spark can produce an explosion.
4- Have you ever produced sparks? If so, explain what happened. Yes I did, when I was near to the TV and it give me a little bit of charge and then I touch another person because we have different charges so it produces a little sparks.
5- Airplanes become charged up when they fly through clouds. Explain why.
´cause they have to cross the clouds so the airplane takes the charge of the clouds and they don´t have any form to throw the energy to the earth, so when it arrive it throw the energy to the earth.
6- What causes a clap of thunder? The energy of the clouds and the energy of the earth found each other and when it happened it produce sound.
- Why tall buildings have lightning conductors?
- Cause is more probable that a spark fall in the tall buildings so they need a conductor to can throw all the energy that can fall in the building and throw it to the earth
Electric circuits:
An electric circuit is a path along which electricity can flow. To make up a circuit you need a battery, a bulb and two wires. The wires and used to join the battery to the bulb. The batteries job is to push an electric current trough the wires and the bulb. The bulb lights up as the current flows I through it.
Meters and switches:
If you want to measure the size of the current, you have to put a meter into the circuit. Current is measure in amperes (A) or amps for short.
The meter for measuring current is called an ammeter.
If you want to turn the bulb on and off easily you should use a switch. A switch works by opening and closing a gap in the circuit. When the switch is turned off, a gap opens up. This stops the flow of current all round the circuit.
When the switch is turned on, the gap is closed this makes a complete circuit and the current can flow.
An electric circuit is a path along which electricity can flow. To make up a circuit you need a battery, a bulb and two wires. The wires and used to join the battery to the bulb. The batteries job is to push an electric current trough the wires and the bulb. The bulb lights up as the current flows I through it.
Meters and switches:
If you want to measure the size of the current, you have to put a meter into the circuit. Current is measure in amperes (A) or amps for short.
The meter for measuring current is called an ammeter.
If you want to turn the bulb on and off easily you should use a switch. A switch works by opening and closing a gap in the circuit. When the switch is turned off, a gap opens up. This stops the flow of current all round the circuit.
When the switch is turned on, the gap is closed this makes a complete circuit and the current can flow.
Currents.
In a series circuit the same current flows through each part of the circuit. There is only one path for the current to flow round. Circuits A and Bare series circuits.
In a parallel circuit the current divides when ir comes to a junction. Part of the currents flows through the other branch. Part of it flows through the other. The bulbs in circuit C and D are joined in parallel.
When two branches have the same resistance, the same current flows through each branch
In a series circuit the same current flows through each part of the circuit. There is only one path for the current to flow round. Circuits A and Bare series circuits.
In a parallel circuit the current divides when ir comes to a junction. Part of the currents flows through the other branch. Part of it flows through the other. The bulbs in circuit C and D are joined in parallel.
When two branches have the same resistance, the same current flows through each branch
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