Electrical Hand Generators
Activities:
Light the bulb.
Crank the generator. The generator is producing electricity. The electricity is lighting
the incandescent (tungsten filament) bulb. Turn the handle in the opposite direction.
Does it still light the bulb?
Operate a Motor
Connect the leads to the terminals of the generator. Unscrew the bulb of the generator.
Connect the leads to the leads of another generator. While only one person turns the
generator handle, watch the handle of the other generator. Does it turn? Does it turn in
the same or the opposite direction from the first generator? Crank in the opposite
direction, does the second handle respond? Don’t crank the first generator but crank the
second one. Does the first handle respond?
Reverse the leads where you have the two generators connected together. Now turn one
generator, does the second generator handle turn in the same direction as before, or in the
opposite direction?
Does the second generator make as many turns as you turn the first generator? Screw the
bulb on the generating machine in. Now turn and see how the second generator responds.
Does it make about the same number of turns as the first generator? Screw in the second
bulb and compare the turns of the handle. Do the bulbs light?
Operate LEDs
Unscrew the light bulbs and disconnect the generators from each other. Attach an LED
(Light Emitting Diode) between the alligator clips. Turn the generator and see if the LED
lights up. Turn the handle in the opposite direction and see if the LED lights up. Turn
the LED so the legs of the LED are connected to the opposite alligator clips. Try lighting
the LED. Connect two or three LEDs between the alligator clips and try lighting them up
by turning the handle both clockwise and clockwise. Does the direction you turn the
handle and the way the LED is arranged between the alligator clips make a difference?
Store Energy
Connect the leads from the generator to the storage capacitor (flat, blue cylinder with two
connecting terminals coming from the top). With the light bulb unscrewed, turn the
handle about five turns and then let go. Does the handle continue moving? Disconnect
one lead from the capacitor. What does this do to the motion of the handle? Reconnect
that lead. What happens? Disconnect the other lead. What happens? Reconnect the
second lead. What happens? Let the generator continue until the charge is all dissipated.
Touch a metal object between the capacitor leads to discharge the capacitor.
With the capacitor discharged and connected to the generator, charge the capacitor with a
certain number of turns of the generator and then let go and see how many turns you get
back from the energy stored in the generator.
Screw in the light and turn the handle to store energy in the capacitor. Stop turning and
see how many turns you get back from the stored energy. Is it the same as before? Why
or why not?
MultiMeter
The MultiMeter is a voltmeter, ammeter, and ohmmeter combined in one device.
Connect the leads from the MultiMeter to the leads from the generator. Turn the
MultiMeter dial to DCV (Direct Current Volts) and to one of the middle values. Crank
the generator. Does it register on the Multimeter? Adjust the dial until you get the best
readout. Notice the variation in the meter reading as the speed of turning differs.
Is the reading positive or negative? Crank in the opposite direction. Did this change the
sign of the meter reading? Connect the alligator clip on the black lead to the red lead and
the red one to the black lead. Crank the generator both directions. Does that affect the
reading on the meter?
Set the MultiMeter to DCA (Direct Current Amperage) and set the dial to a middle value.
Crank the generator and adjust the dial to get a good reading on the dial. Is the reading
very consistent? What happens when the crank is turned the opposite direction? What
happens when the light bulb is screwed in or screwed out?
The ohmmeter part of the MultiMeter just measures electrical resistance. If you set the
dial in the resistance ranges (lower left area near the blue circle), touching the leads
together will give a resistance pretty close to zero ohms (since you are only measuring
the resistance of the copper wire in the leads). When the meter gives a “1” on the far left
side, it means the resistance is too small to be measured using that scale, go to a more
sensitive scale. Connecting the leads to the generator (but don’t turn the handle) will give
the resistance of the wires and the coils of wire inside the generator. You may have to
turn to the most sensitive scale, which is the 200 scale. Screw the bulb in and compare
the resistances with the bulb in and out. Why is it less when the bulb is screwed in? (in
parallel, the total resistance drops)
CAUTIONS:
The Hand Generator is not made for student use. Students will want to go as fast as
possible. They will not be concerned whether there is a load or not. To get maximum
life from your generator, 1) Always have the circuit closed with the light bulb screwed in
or the leads touching, 2) Turn the handle at a reasonable rate, fast enough to observe what
you are testing, but not excessively, 3) Make repairs when necessary. The nylon gears
wear where the brass gears are so it will make noise. Be gentle, but it should still work.