How Does Electricity Travel From the Wall to the Lamp?

Lamps of all shapes and sizes are illuminated by a similar process.

For the non-techie, the topic of how electricity travels from the wall to the lamp can seem intimidating. If this is the case, it might help to think of a light switch like a water faucet. Behind the faucet (switch) is a source. In this case, the source, instead of water, is electricity. Instead of a pump that provides pressure to make the water flow, you have a power generating station that provides the impetus to push the electricity along the wires to your house, where it waits patiently at the outlet for you to plug in your lamp.

Electrical Switch

You could think of an electrical switch as a dam holding water behind it in a reservoir. When the flood gates are opened, water flows through and down the spillway. An electrical switch functions in much the same way. When it is in the "on" position, electricity is allowed to flow to the plug, available for household use. Turning the switch to the "off" position interrupts the flow of electricity, leaving the outlet dead.

Energy Path

With the light switch turned on, electricity sits at the outlet waiting for a demand to be made. In this case, the demand is the action of plugging the free end of your lamp cord into the outlet. The metal prongs at the end of the cord are what complete the circuit and allow electricity to flow from the outlet down the length of the cord and into the bottom of the bulb that powers the lamp. Electricity has now traveled from where it was generated to the point where it will be converted into a practical use.

Bulb

The way a bulb works can be described simply or with more complexity. Simple is the favored choice here. There are two metal contacts at the base of the bulb. Attached to each is a support wire connected together by a filament inside the bulb. Electricity travels up one wire, through the filament, and back down the other wire. A bunch of technical stuff happens inside the filament, which essentially adds up to atoms smashing into one another, creating energy released as visible light.

Considerations

Most lamps have a switch of their own built in which functions the same as an on/off light switch on a wall. This arrangement allows the user to control the electrical flow at the lamp itself rather than at the wall. The process works by leaving the wall switch on all the time, which allows electricity to flow through the cord to the lamp. With the lamp switch on, electricity flows into the bulb, lighting it up. When switched to off, electrical energy is damped at the lamp instead of the outlet.

References

• Northwestern University: How Lights Work; Mathew O'Connor, January 2011
• Occupational Safety and Health Administration: How Electricity Works
• PacificPower.net: How Electricity Works
• ACME How-To: How an Electric Light Switch Works