Question

EM 98 A model for circuits Part 1: Current and resistance C. Light a bulb using a battery and a single wire. Observe and record the behavior (ie., brightness) of the bulb when objects made out of various materials are inserted into the circuit. (Try materials such as paper, coins, pencil lead, eraser. your finger, etc.) What is similar about most of the objects that let the bulb light? D. Carefully examine a bulb. Two wires extend from the filament of the bulb into the base. You probably cannot see into the base, however, you should be able to make a good guess as to where the wires are attached. Describe where the wires attach. Explain based on your observations in parts A-C. On the basis of the observations that we have made, we will make the following assumptions: 1. A flow exists in a complete circuit from one terminal of the battery, through the rest of the circuit, back to the other terminal of the battery, through the battery and back around the circuit. We will call this flow electric current. 2. For identical bulbs, bulb brightness can be used as an indicator of the amount of current through that bulb: the brighter the bulb, the greater the current. Starting with these assumptions, we will develop a model that we can use to account for the behavior of simple circuits. The construction of a scientific model is a step-by-step process in which we specify only the minimum number of attributes that are needed to account for the phenomena under consideration.

Answer 1

C) The bulb glows when connected to some objects. But it does not glow when some objects like eraser, wood, plastic, etc... are used to complete the circuit. Such materials are called insulators.

Also, there was a difference in brightness of the bulb when some objects were used.

For example, when a thick coin was used, the bulb glowed bright. When a thin and long wire was used, the brightness of the bulb decreased. When the pencil lead was used, the brightness of the bulb was less.

This is because, the resistance to electricity of different objects are different. When the resistance is high, the current decreases, and the bulb glows less bright.

Most of the objects that helped the bulb to glow are metals. Generally, metals have high electrical conductance. So, the brightness of the bulb would be high.