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Home Concept Builders Electric Circuits Light Bulb Anatomy Help Help 6

Light Bulb Anatomy - Questions 6 Help

For a light bulb to light, charge must enter the threaded side of the bulb and exit out the bottom tip of the bulb OR enter the bottom tip of the bulb and exit out the threaded side of the bulb. As long as a bulb is connected in this manner to the pathway that leads from the positive terminal of the cell to the negative terminal of the cell, the bulb will be lit.

There are three similar versions of this question. Here is one of the versions:

Version 1:
Determine the pathway that charge takes from point A to point B. Tap on the diagram to toggle through the choices.

Which, if any, of the bulbs will light?
a. Bulb 1 Only
b. Bulb 2 Only
c. Both Bulbs
d. Neither Bulb

Requirements of a Circuit
It is sometimes said that there are two requirements for a circuit: (1) There must be a source of energy such as a battery or cell. (2) There must be a complete, conducting path that leads from the + to the - terminal fo the energy source. If a light bulb is part of this conducting path, then the light bulb will light.


How a Light Bulb Lights
A light bulb will light if charge flows through its filament. The filament is the curled wire that is located inside the glass bulb of a light bulb. The filament is connected to the side of the light bulb by a wire that supports one of its ends. The other end of the filament is supported by a wire that leads to the bottom tip of the bulb. As long as the bulb is arranged such that charge enters its side and exits out its bottom OR enters at the bottom and exits out the side, the light bulb will light. Carefully inspect each diagram to see if the light bulb is arranged in one of these two ways.


Determining the Pathway
Starting at Point A, observe the wire that is attached to the first bulb. Suppose that the wire touches the side of the bulb; see if the bottom of the bulb is attached to another wire or another bulb. If it is, then charge can follow a pathway up to the glass bulb, through the filament, and back down to the bottom of that bulb. If it isn't, then charge will not pass through the filament but instead will travel across the metal side to whatever is connected on the opposite side of the bulb. The same type of thinking can be applied to bulb 2 until the charge exits through the wire to Point B.

Try these links to The Physics Classroom Tutorial for more help with understanding what makes charge flow through a circuit:

What is an Electric Circuit?

Requirements of a Circuit

Concept Builder Teacher Notes Directions