S: Electric Current for the operation of electric Lighting
FC: Electric current for the operation of electric lighting
1: One practical and popular use of electric current is for the operation of electric lighting. The simplest form of electric lamp is a tiny metal "filament" inside of a clear glass bulb, which glows white-hot with heat energy when sufficient electric current passes through it. Like the battery, it has two conductive connection points, one for electrons to enter and the other for electrons to exit. Connected to a source of voltage, an electric lamp circuit looks something like this: | Filament:filamento bulb:lamparita conductive: condutores source: fuente
2: As the electrons work their way through the thin metal filament of the lamp, they encounter more opposition to motion than they typically would in a thick piece of wire. This opposition to electric current depends on the type of material, its cross-sectional area, and its temperature. It is technically known as resistance. | encounter: encuentran resistance: resistencia conductors: conductores Insulators: aislantes joining: union
3: This resistance serves to limit the amount of current through the circuit with a given amount of voltage supplied by the battery, as compared with the "short circuit" where we had nothing but a wire joining one end of the voltage source (battery) to the other. | What does resistance do?
4: When electrons move against the opposition of resistance, "friction" is generated. Just like mechanical friction, the friction produced by electrons flowing against a resistance manifests itself in the form of heat. | friction: friccion flowing: fluyendo resistance: resistencia | What happens when electrons move against the opposition of resistance?
5: The concentrated resistance of a lamp's filament results in a relatively large amount of heat energy dissipated at that filament. This heat energy is enough to cause the filament to glow white-hot, producing light, whereas the wires connecting the lamp to the battery (which have much lower resistance) hardly even get warm while conducting the same amount of current. | dissipated:disipada white hot: candente | How is light produced?
6: As in the case of the short circuit, if the continuity of the circuit is broken at any point, electron flow stops throughout the entire circuit. With a lamp in place, this means that it will stop glowing:
7: As before, with no flow of electrons, the entire potential (voltage) of the battery is available across the break, waiting for the opportunity of a connection to bridge across that break and permit electron flow again. This condition is known as an open circuit, where a break in the continuity of the circuit prevents current throughout. All it takes is a single break in continuity to "open" a circuit. Once any breaks have been connected once again and the continuity of the circuit re-established, it is known as a closed circuit. | What is an open circuit? | potential: potencia bridge across: puentiar prevents: previene established:establecido closed circuit:circuito cerrado
8: What we see here is the basis for switching lamps on and off by remote switches. Because any break in a circuit's continuity results in current stopping throughout the entire circuit, we can use a device designed to intentionally break that continuity (called a switch), mounted at any convenient location that we can run wires to, to control the flow of electrons in the circuit: | switching:prender remote: mounted: montada wires:cables | switching: prender remote switch: interrupor throughout: en todo mounted: instalada wires: cables run: pasar
9: What happens if there is a break in a circuit's continuity?
11: True or False 1. RESISTANCE is the measure of opposition to electric current. 2. A short circuit is an electric circuit offering big resistance to the flow of electrons. 3. An OPEN CIRCUIT is one where the continuity has been broken by an interruption in the path for the electrons to flow. 4. A CLOSED CIRCUIT is one the is incomplete, with no continuity throughout. 5. A device designed to open and close a circuit under controlled conditions is called a BULB.