light bulb process

8/6/2019 Light Bulb Process

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Sam Goldstein

7/26/11English 202C

Josh Smith

Illuminating a Light Bulb

For readers with a basic understanding of electricity and circuits. Knowledge of beginner

chemistry is needed for one calculation, but it is not integral in understanding this paper.

Introduction

The simple act of flipping a light switch either up or down does not create light inside a

light bulb; the flipping action merely completes an electrical circuit. Whether the light switch is abasic up/down switch, a push in switch, or a turning switch, the action involved simply

completes a circuit. The electrical circuit that the light bulb is a part of has many different parts;

the circuit being analyzed is a basic DC (direct current) circuit that has one power source, and

one resistor.

Components

1) DC Power Source

• A DC power source can either be a battery or an electrical outlet that suppliesa direct current.

• Electrical outlets usually power household lights.2) Current

• Current is the flow of charged particles through a wire.

• A direct current flows in one distinct direction from the positive terminal of the power source to the negative terminal.

3) Resistor

• A resistor literally resists the flow of charge and is the light bulb in this case.

• Energy builds up at the resistor.

Light Bulb

Figure 1: Outline

of DC circuit.

The resistor is the

light bulb.

Simple DC Circuit .Digital image. School

For Champions. Web.

24 July 2011.

<http://www.school-for-

champions.com/scienc

e/images/elect_ohms_l

aw-dc_circuit.gif>.



Process

When a light switch is turned off, electrically speaking the circuit is open. The pictureabove shows a closed DC circuit. An open circuit has a break anywhere along one of the wires.

When the light switch is flipped on, the circuit is closed and the bulb is illuminated. The process

of lighting starts immediately after the circuit is closed.

When the circuit is closed, charged particles flow on the wire from the positive terminalof the power source to the negative terminal moving through anything in its path. In the case of

the given circuit above, the charge flows up, then to the right, then down through the resistor.The resistor is the light bulb so this is the spot where lighting happens. Resistors are built so that

as charge flows through them, a buildup of energy in the forms of light and heat is made.

The wires from the basic circuit in Figure 1 enter and leave the resistor that is marked

with a jagged line. In reality, the wires connect at a piece of metal that conducts electricity. The

light bulb is then screwed into the piece of metal to accept the flow of charge. The charge flowsup wires into the light bulb. Once charged particles are in the light bulb, they flow through a

filament labeled 3 in Figure 2. The filament is made up of atoms that have free electrons. Free

electrons are in conductors and have the ability to change energy states easily.

Figure 2: Light Bulb Parts

Incandescent Light Bulb . Digital

image. Wikipedia. Web. 24 July2011.

<http://en.wikipedia.org/wiki/Incandescent_light_bulb>.

Figure 3: Wires connecting to metal conductor. Light bulb screws into metal piece and charges begin to flow into the bulb.

Incandescent Light Bulb. Digital image. Wikipedia. Web. 24 July 2011. <http://en.wikipedia.org/wiki/Incandescent_light_bulb>.

Rubber Outdoor Light Bulb Socket . Digital image. Ooga Lights. Web. 25 July 2011. <http://www.oogalights.com/Leviton-875-55-Rubber-Outdoor-Light-

Bulb-Socket-Pig-Tail-Wires.aspx>.



The changing of electron energy levels is how light is created. When an electron absorbs

energy, it moves to a higher energy state. As it continues to move freely, it eventually losesenergy and moves down energy levels. The transition from high energy to low energy emits a

photon, which is an electron that gives off light. Each photon is emitted with a different energy

that is inversely proportional to wavelength. The human eye can only see light in the visible

spectrum of light which from 400-700 nanometers in wavelength. If the energy of an electron’stransition is known, the wavelength can be calculated by the formula:

ℎ =(′ )( ℎ)

• Plank’s Constant 6.626 x 10-34 (kg*m2)/s2

• Speed of Light 3 x 108 m/s

• Wavelength found is in meters. Convert to nanometers.

• Energy is in units of joules.

When the charged particles enter the filament, 3, the charges make contact with the free

electrons of the filament causing energy to be exchanged. Each energy exchange causes anelectron to get excited to a higher energy level. After a very short period of time, the free

electrons move back down to the ground state (low energy). This transition from high to low

energy emits a photon. If the transition has a wavelength in the visible spectrum, the human eye

sees a photon of white light. The charge continues its path on its way back to the negativeterminal of the battery. This process continues to happen as long as the circuit is closed. If charge

can make its way to the resistor, energy will be transferred. As long as the light is switched on,

and the circuit is closed, this process will continue indefinitely. Each emission of a photon keeps

the light bulb bright.

Conclusion

Initially, the light switch is off and the circuit is open; there is no flow of charge throughthe resistor. When the switch is closed, charge flows in one direction from the positive terminal

of the power source to the negative terminal encountering anything in its way. As the chargereaches a resistor that is in the form of a light bulb, charge flows into the bulb. Once the moving

charges encounter the free electrons in the filament, energy is transferred and free electrons are

excited to higher energy levels. Over time, the free electrons lose energy and they fall down totheir ground state energy. This process emits a photon of a certain energy and wavelength. If the

wavelength is in the visible spectrum, the human eye sees light. Enough photons per second are

emitted in a light bulb to keep it constantly illuminated. The charge then continues back to the

power source and the process continues until the circuit is open; the light switch is off.

light bulb process

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