Download Electricity is Exciting! for Fifth Graders

Electricity is Exciting! for Fifth Graders
Warning! Electricity can be dangerous. ALWAYS have an adult help you experiment.
NEVER, ever play with the electric outlets at home!
Charge
An Electron
Voltage
“Stack” of Charges
Current
Moving (Flowing) Charges
1. Charges and Currents
a. Wires are made of copper. Copper
Electrons are Green.
b. Some Copper electrons from the wire get
stuck in the potato when the current moves
through the potato. What color is the spot
near the positive part (anode) of the battery?
+ is _____________
c. What color is the spot near the negative (cathode)
part of the battery? - is ____________
2. Electrical Engineers use a Digital Voltmeter Meter (DVM) for measuring
Get your (yellow) DVM ready to
measure Voltage:
a. Connect the Red DVM Cable to
the VmA hole.
b. Connect the Black DVM Cable
to the Com hole.
c. Turn the Dial in the middle to the
DCV 20 Spot.
3. Measuring Voltage:
Measure the Voltage of one Battery:
a. Touch the Red DVM cable to +
terminal of the battery (the top).
(Push hard enough.)
b. Touch the Black DVM cable to
the – terminal of the battery (the
bottom).
c. What is the Voltage of one
battery? V1=__________ Volts
d. Now measure the other battery.
What is its voltage?
V2=_____________ Volts
4. Voltages in Series Add
What should we get?
a. Write down V1 and V2 that you measured before.
b. Add them up.
Now tape the batteries together in Series as shown.
c. Measure the voltage of the two batteries in series. Write your answer here.
Compare your results. Are your calculations and measurements the same?
They should be close. Sometimes they are not exactly the same, because
measurements are never perfect.
4. Resistance
Resistance slows the flow of current. Resistors “eat” charges and turn them into heat.
a. Find the 100  resistors. They have four stripes (brown-black-brown-gold).
b. Find the 1000  resistors. They have four stripes (brown-black-red-gold).
Get your DVM ready to measure resistance.
c. Turn the DVM dial to 2000 .
d. Connect (touch hard) the DVM cables to each side of the resistor.
Measure your resistors
e. Measure the 100  resistors and write their resistance above.
f. Measure the 1000  resistors and write their resistance above.
Experiment: Does it matter which way you turn the resistor around?
5. Resistors in Series
a. Electrical Engineers use Protoboards to Design and Test their Circuits.
When two wires are in the same row, like these are, they are connected inside the
protoboard.
b. Connect two resistors in series. Calculate and measure the series resistance.
c. When you put two resistors in series, is the total resistance larger or smaller than the
original resistors? __________________
6. Resistors in Parallel
Resistors in parallel ( || ) are side-by-side on the protoboard.
They combine in a different way, shown above
Experiment with several different resistors in parallel.
R1
100
1000
100
R2
100
1000
1000
R1||R2 Calculated
50
500
90.9
R1||R2 Measured
Is the resistance of two parallel resistors always:
a. Larger than both resistors
b. Smaller than the biggest resistor
c. Smaller than either resistor
7. Light Emitting Diode (LED) Circuit
An LED is a resistor that turns charges
into light.
a. Find the FLAT side with the
BLACK leg, and put it in the
protoboard as shown.
b. Tape wires on the ends of your
batteries.
c. Connect the + part of the battery to
the round side of the LED.
d. Connect the – part to the flat side of
the LED, as shown. What happens?
8.How can you control the light from the LED?
a. Put a 1000 resistor in series with the
LED as shown.
What happens to the light?
b. Challenge: Try different
combinations of resistors in series and
parallel until you can get the most light
from your LED and the least light from
your LED.
Reducing the current through the LED
will reduce the light it puts out.
You can reduce the current by putting a
resistor in series with it.
Hint: Ohm’s Law (like the law of
gravity for electrical engineering) say:
Current = Voltage  Resistance.
For less current, should you use more or
less resistance?
9. Sum of Voltages
V2
V4
In a circuit, all of the voltages will always add up to the voltage you put on the circuit.
Test this theory:
a. Connect three resistors in series with the LED.
b. Measure the voltage across each resistor (and the LED) in the circuit. Be sure you
only connect the DVM across the resistor where you are measuring the voltage
(see V2, for instance)