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Unit 10: Electricity Page 23

streets for electricity – they allow

electrons to flow one way but not 2. Check the connections. Are
the other. they clipping their alligator wire
to the metal tip on the wire, or
Remember when you scuffed along
to the plastic insulation? Which
the carpet? You gathered up an
conducts electricity better?
electric charge in your body. That

charge was static until you zapped
3. Check the direction of the LED
someone else. The movement of
(Light Emitting Diode). The LED
electric charge is called electric
is a one-way street for
current, and is measured in
electricity. If it’s in backwards,
amperes (A). When electric current
disconnect it, flip it around, and
passes through a material, it does
stick it back in the circuit. This
it by electrical conduction. Let’s
is an excellent lesson in
make a set of circuits using our
‘polarity’ (positive and
components. Here’s what you do:
negative). LEDs are picky about
1. Insert fresh batteries into your plus and minus – it matters
battery holder.
which way you hook it up.
2. Spread the LED leads a bit apart
so you can clip one alligator 4. Change out the wires.

wire to each lead without Sometimes wires have small
touching the other. breaks near the clip ends which
you can’t see because they are
3. Clip an alligator clip wire from
underneath the insulation.
one battery wire to one LED
Change out one wire at a time
lead wire, and repeat for the
so you’re sure to find the
other side.
culprit. Take it apart and fix it
4. Your LED should light up. later.

Troubleshooting: Here’s how to
Try substituting buzzers, motors,
help if their circuit doesn’t work:
and other components for the LED.
1. Check the batteries. Are they in A nice touch is to see if your
the right way? You’d be student can get all the LEDs and
surprised how often this things to activate at the same
happens. Are the batteries time!
fresh? Most LEDs require at

least 2.2V to illuminate.

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