Elenco Snaptricity&reg - Manual (Page 21)

Pushing Electricity Project #11
-20-
5V
5V
Educational Corner:
Build the circuit and connect the red jumper wire as shown.
Set the meter (M5) to the 5V setting and the slide switch
(S5) to position C at first.
Assembly
Read the battery voltage on the meter (the top scale), it
should be about 4.5V. The lamp will be off.
Flip the switch to position B; the lamp lights and the voltage
drops a little. (To learn why the voltage drops now, ask
Snappy.)
Move the red jumper wire from position A on the switch to
position B. The battery voltage is the same here because
none is lost across the switch.
Now flip the switch to position C (OFF); the voltage at the
lamp drops to zero and it shuts off.
Operation
Electricity is the movement of sub-atomic charged particles (electrons) through a material due
to electrical pressure across the material, such as from a battery.
The electrical pressure exerted by a battery or other power source is called voltage and is
measured in volts (V, and named after Alessandro Volta who invented the battery in 1800).
Notice the “+” and “–” signs on the battery. These indicate which direction the battery will “pump”
the electricity.
Circuits need the right voltage to work properly. For example, if the electrical pressure to a lamp
is too low, then the bulb won’t turn on; and if too high, then the bulb will overheat and burn out.
The electric current is a measure of how fast electricity is flowing in a wire, just as the water
current describes how fast water is flowing in a pipe. It is expressed in amperes (A, named
after Andre Ampere who studied the relationship between electricity and magnetism) or
milliamps (mA, 1/1000 of an ampere).
Record the voltage you measured here, it will be used in project 13:
Snappy says: the battery voltage drops when the lamp is connected because
the batteries have trouble supplying as much electricity as the lamp would like.
Remember that a battery produces electricity from a chemical reaction. Not
only is there a limited amount of the chemicals in a small battery (batteries
slowly get weaker as you use them), but also not all of the material can react
together at the same time.