Exploratories

A Simple Electric Circuit

Purpose
:

To demonstrate what is needed to produce a simple electric circuit.

Materials:

1.5 to 6 volt battery; light bulb and socket; at least two pieces of hookup wire.

Procedure:

1. Attach a piece of hookup wire to the battery and show that the bulb will not light if the wire is attached to either terminal of the light bulb or either terminal of the battery.

2. Attach two pieces of hookup wire to the battery, one to each terminal. Show that
the bulb lights only when one wire is attached to one terminal of the bulb and the other wire to the second terminal of the bulb. Point out that in an electric circuit there must be a path from the source to the appliance, through the appliance, and back to the source. It often helps to point out that the word circuit has the same root as the word circle.

Summing Up:

Because charge is conserved, current must flow equally in all points of the circuit. The source receives as much current at one terminal as leaves from the other.

D.C. Circuits Terms

Terms to define

circuit - a closed conducting path around which charge or matter can flow.

current - the flow of electric charge or matter from one place to another.

conventional current - conventionally taken to mean that positive charge flows from a positive to negative direction; in metals where only electrons flow, this is called negative electron current.

EVERYDAY CONNECTIONS

Why won't your car start if one of the terminals falls off the battery?

Discuss the ways that water currents are similar to electric currents.

Electron Speed

When you turn the ignition key in an automobile, you complete a circuit from the negative battery terminal through the electric starter and back to the positive battery terminal. This is a DC circuit and electrons migrate through the circuit in a direction from the negative battery terminal to the positive terminal. About how long must the key be in the ON position for electrons starting from the negative terminal to reach the positive terminal?
a) A time shorter than that of the human reflex turning a switch on or off
b) 1/4 seconds
c) 4 seconds
d) 4 minutes
e) 4 hours