How Do You Charge a Cell Phone? | Design Squad

(whirring sound) I’m Nate from Design Squad. I’m going to repurpose this
electric screwdriver to make it into an hand-cranked
cell phone charger. (whirring) I’m going to put in this hand
crank that I made. I pull the trigger, and you can
see the crank going all around. So when we’re doing this,
we know what’s happening is there’s electric power going
from the battery through the motor into the
rotational energy in the front. (motor whirring) Now, what would happen if we
cranked it backwards? (quick whirr) See the cool thing about
electric motors is they work both ways. The motor would do the same
thing as usual except in the
opposite direction. It would take
the mechanical energy and turn it into
electrical energy. (whirring) This hand crank
lets me crank by hand with a lot of torque,
or turning effort. So I’m working real hard to spin
the gear box around. And the gear box is turning that
torque into speed. At the other end, it’s going to
spin the motor really fast. I’m hooking up this LED… (electrical whirring) Yeah! See that? We are generating electricity. Why would I want to make
a hand crank generator when I could just plug in my
phone to charge it? What if my phone was dead and I
didn’t have a plug available? Like if I was camping? Or if there was an emergency? Plus, I’m learning
a lot of useful stuff about motors and generators for next time I want
to build something like this. So this is a digital multimeter,
which measures how much electricity
we’re generating. (whirring) Cool. I’m getting 3 volts. To charge my cell phone,
I need to get five volts. What does that mean? I’ve got to crank faster. All right. 5.1, 5.2– This is how fast I need to crank if I’m going to charge
my cell phone battery. Pretty much all
I have left to do is attach the wires together
and plug it in. And we’re ready to try it. (whirring) I’m at 5.3 volts, the phone has come on, and I have
a charging symbol on it. I’m generating electricity in
exactly the same way as, say, a wind turbine would. But instead of the wind cranking
the blades around, my hand is cranking
the crank around. It’s mechanical power
driving a motor that then generates electricity because we’re
running it backwards. Look around and see what kind of
stuff you can repurpose. (whirring) Now I gotta sit here doing this
for a couple of hours. (laughing) No problem.