BACKGROUND:
Electricity is the movement of
electrons which creates a current. A circuit is a closed or undisturbed
path of electrons through a wire made up of material that conducts
electricity. A bulb in a circuit will only light if it is in a closed
circuit.
Electricity will not go through all
materials. If electricity goes through and completes a circuit, it is
called a conductor. If electricity doesn't go through to complete the
circuit, it is called a non-conductor (or insulator). Insulating
materials have electrons so closely bound to the nucleus of the atom
that a steady electric current is greatly reduced. In a conductor,
usually metals, the "free" electrons can move from atom to
atom to permit passage of an electrical current. If there is a
restricted flow of electrons through special conditions, it is called a
semiconductor. In this lab, students can only detect a conductor or
nonconductor.
Students will try and determine how
to complete a circuit. They have learned about parallel and series
circuits in the third grade. If they have forgotten, review those labs.
Parallel and series circuits have to do with the direction of the flow.
In series circuits, the flow goes from one light to another light. The
lights get progressively dimmer because there is not enough voltage to
light them all brightly. Only a parallel circuit can maintain the
voltage to each bulb at the same intensity.
PROCEDURE:
- Explain to students that they are
going to be working with electricity in the form of a current. The
energy that creates the current is contained in the battery. This energy
is stored in the form of chemical energy.
- Explain how electricity has made
our lives easier. By operating machines, electricity has freed humans
from otherwise tedious tasks. Also discuss how our lives would be
affected if electricity could no longer be produced. Have students
create a list of things that will and will not work without electricity.
Students will be surprised at the amount of machines that use
electricity.
- This lab looks at the circuit by
investigating the battery. A battery is the energy source that creates
free electrons. There are several types of batteries on the market, but
no matter which battery you use, the information needed will be on each
battery. The size of the battery is also labeled. Each battery, no
matter how large, is one cell or a series of cells. One cell gives 1.5
volts of electricity. A six-volt battery will have a series of 4 cells
of 1.5 volts. If available, show examples of other types of batteries.
- For this lab, give each group a
battery holder, 2 batteries, a miniature light bulb and different
conductors and non-conductors that are provided in the module. You may
want to add different materials you have available.
- ANSWERS:
Exercise I
1. D
2. 1/2 volts (some may be 1.5 volt)
3. Chemicals that produce free electrons
4. Note: the side with the "bump" is always positive
5. If the light bulb brightens, then the battery is charged.
6. Same thing happens. You can reverse wires and the same reaction
occurs.
7. A circuit
8. Because the flow of electrons goes like the arrows in the diagram.
9. The bulb should be a little brighter.
10. Add them up 1.2 + 1.2 = 2.4 volts
Exercise II
You can determine if a substance conducts
electricity by testing it with a set up like a circuit. If the bulb
lights up, it is conducting electricity.
