Elenco Snaptricity&reg - Manual (Page 23)

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What’s An Ohm? Project #13
1A
1A
Snappy says: the Ω
symbol is the last letter in
the Greek alphabet and
is pronounced Omega.
Educational Corner:
The resistance of a circuit represents how much it resists
the electrical pressure (voltage) and limits the flow of
electric current. The relationship between voltage, current,
and resistance is the most important one in electronics. It
is known as
Ohm’s Law (after George Ohm who
discovered it in 1828):
When there is more resistance, less current will flow unless
you increase the voltage. Resistance is measured in ohms.
The symbol used for an ohm is
Ω .
Using the voltage measurement you made in project 11 and
the current measurement you made here, you can calculate
the resistance of the lamp. It is usually 15-20 ohms.
The other parts in the circuit (switch, meter on 1A scale,
blue snap wires, and batteries) also have resistance but
these are much smaller.
Note: Your actual results may vary. Your M5 meter is a
simple meter; don’t expect it to be as accurate as normal
electronic test instruments.
What is Resistance? Take your hands and rub them
together very fast. Your hands should feel warm. The
friction between your hands converts your effort into heat.
Resistance is the electrical friction between an electric
current and the material it is flowing through; it is the loss of
energy from electrons as they move through the material.
Voltage
Resistance
Current =
The “ power ” of electricity is a
measure of how fast energy is
moving through a wire. It is
expressed in
Watts (W, after James
Watt for his work with engines). It
is a combination of the electrical
voltage (pressure) and current:
Power = Voltage x Current
OR
Using the voltage and current
measurements you made, you
can calculate the power of the
lamp. It should be about 1 watt.
Compare this to the light bulbs in
your home, which are usually
about 40-100 watts.
Voltage x Voltage
Resistance
Power =
Electric
Paths
= Current x Current x Resistance
Build the circuit shown. Set the meter (M5) to the 1A setting.
Assembly
Set the slide switch (S5) to position B to measure the
current through the lamp (L4).
Operation