An electrical current flows from one metal contact to the other when a light bulb is connected to an electrical power supply. The filament warms up as the current flows between the wires and the filament, causing it to emit photons, which are little packets of visible light. The photons create more electrons on the outer surface of the filament, which increases the flow of current.
The electron flow through the filament creates more photons, which continue the cycle. This continuous creation and destruction of photons keeps the filament at a high temperature, which allows more electrons to move across it per second. This effect is called "thermionic emission."
A third type of emission is also seen with hot objects: photonic emission. When atoms or molecules relax after being excited by a photon, they can jump back down in energy level tracks called "bands". Under the right conditions, they will do so without re-emitting any light because there are no available free electrons with which to pair up (except for the electrons in atoms in general, but that's another story). Such relaxation processes are common in solids like glass or plastic, and they can account for some light emissions we see from hot objects. But these are not thermionic emissions; instead, they result from phonons (quantum mechanical vibrations) interacting with the object's structure.
Finally, we have electronic emissions.
The lightbulb is incandescent. Incandescent lamps generate light by heating a narrow strip of material known as a filament with electricity. The filament inhibits the passage of electrons, which causes the filament to heat up and light. As the filament gets hotter it emits more ultraviolet radiation and less visible light, which is why incandescent bulbs are dimmer as they burn out.
Filaments decay over time due to thermal stress and aging, so they need to be replaced about once every 1,000 hours. However, if they are replaced before that then they will burn out too soon and fail lamp tests, so it's important to know how to test them.
Incandescent lamps come in many different sizes from small tea lights to large floor lamps. All operate on the same basic principle but use different sized filaments to produce different levels of brightness.
The filament is surrounded by an envelope of glass and sealed inside a metal casing. When electricity enters the casing via the plug it flows through two wires connected to the electrodes of the bulb. These wires are called leads because they lead into or out of the bulb. Leads can be made of copper or other conductors for this purpose. Inside the body of the lamp there is an electric circuit which includes the filament, along with its housing and insulation.
The metal case and the bulb's tip are both connected to the circuit, making a closed circuit. As a result, energy may travel via the wires in the circuit to the filament, causing the bulb to light up. The voltage applied to the wire determines how bright the bulb will be when it is turned on.
There are three ways for a circuit to complete a loop so that current can flow: through a resistor, which creates heat; with a magnetic component such as a transformer or inductor; or by itself. A simple switch will usually connect or disconnect two circuits from each other, creating a new circuit whenever you turn off the switch. This keeps current flowing all the time, even if one of the parts is not needed (for example, when you shut off the switch, you have destroyed the function of a light fixture).
In most cases, your house is powered by electricity that comes into your home through a wall socket. This electric power travels down conductors inside these walls and floors until it reaches the next piece of wiring that carries its signal away from the origin of the power supply. At this point, the conductor is called a hot wire because it is always kept at a high temperature when electricity flows through it. Any other conductor carrying an electrical signal back to the source of the power is called a neutral wire because it does not carry heat along with it when electricity flows through it.
There is a closed (or complete) circuit with the bulb when the wires in the circuit are connected to the metal casing and metal tip of the bulb. The filament will allow electricity to pass through it, enabling the bulb to light up. If the connection between the casing and the filament were broken, there would be no path for current to follow, so the bulb would not light up.
Light bulbs can fail for many reasons. If the glass breaks, the entire bulb needs to be replaced before using it again. If the filament goes out, the whole bulb should be replaced before using it again. Filaments can also burn out due to excessive heat. This could happen if you used the bulb in a location where it was exposed to direct sunlight for an extensive period of time. In this case, the bulb needs to be removed from the fixture and replaced.
First, turn off the power at the main fuse panel or circuit breaker box. Next, locate the metal cage that holds the bulb, and remove it. Finally, remove the old bulb by pulling it straight out of the socket. Be sure to keep track of which one went in first if you need to reinstall it later. When replacing bulbs, try to use the same type of bulb as before.
A light bulb is an extremely thin tungsten wire encased in an inert gas environment. When a current flows across a wire, electrical energy is converted to heat, which causes the wire to become incredibly hot – about 1000oF! Objects this heated emit visible light, and there you have your light bulb.
The current flowing through the light bulb creates electromagnetic fields that interact with the surrounding magnetic field, producing light. The intensity of the light depends on how much current is running through the bulb.
In fact, almost all electric devices produce some amount of radiation as they work: radios, televisions, hair dryers, and even power switches can be sources of radiofrequency (RF) radiation. This type of radiation isn't dangerous, but it does mean that using such devices increases your exposure to these fields. Modern electronics are very efficient sources of energy, so even if you use many devices at once, you will still get only slightly higher levels of radiation from our environment than someone who uses less equipment.
The main thing to remember is that all objects containing atoms have the potential to radiate energy, and some do so very efficiently. Thus, you should avoid standing too close to a microwave oven or holding a light bulb directly above your head!
However, most forms of radiation we encounter in daily life aren't harmful.