<s>
A	O
lemon	B-Algorithm
battery	I-Algorithm
is	O
a	O
simple	O
battery	O
often	O
made	O
for	O
the	O
purpose	O
of	O
education	O
.	O
</s>
<s>
Typically	O
,	O
a	O
piece	O
of	O
zinc	B-Application
metal	O
(	O
such	O
as	O
a	O
galvanized	O
nail	O
)	O
and	O
a	O
piece	O
of	O
copper	O
(	O
such	O
as	O
a	O
penny	O
)	O
are	O
inserted	O
into	O
a	O
lemon	B-Application
and	O
connected	O
by	O
wires	O
.	O
</s>
<s>
The	O
lemon	B-Algorithm
battery	I-Algorithm
is	O
similar	O
to	O
the	O
first	B-Architecture
electrical	I-Architecture
battery	I-Architecture
invented	O
in	O
1800	O
by	O
Alessandro	O
Volta	O
,	O
who	O
used	O
brine	O
(	O
salt	O
water	O
)	O
instead	O
of	O
lemon	B-Application
juice	O
.	O
</s>
<s>
The	O
lemon	B-Algorithm
battery	I-Algorithm
illustrates	O
the	O
type	O
of	O
chemical	O
reaction	O
(	O
oxidation-reduction	B-Operating_System
)	O
that	O
occurs	O
in	O
batteries	O
.	O
</s>
<s>
The	O
zinc	B-Application
and	O
copper	O
are	O
called	O
the	O
electrodes	O
,	O
and	O
the	O
juice	O
inside	O
the	O
lemon	B-Application
is	O
called	O
the	O
electrolyte	O
.	O
</s>
<s>
There	O
are	O
many	O
variations	O
of	O
the	O
lemon	B-Application
cell	O
that	O
use	O
different	O
fruits	O
(	O
or	O
liquids	O
)	O
as	O
electrolytes	O
and	O
metals	O
other	O
than	O
zinc	B-Application
and	O
copper	O
as	O
electrodes	O
.	O
</s>
<s>
There	O
are	O
numerous	O
sets	O
of	O
instructions	O
for	O
making	O
lemon	B-Algorithm
batteries	I-Algorithm
and	O
for	O
obtaining	O
components	O
such	O
as	O
light-emitting	O
diodes	O
(	O
LEDs	O
)	O
,	O
electrical	O
meters	O
(	O
multimeters	O
)	O
,	O
and	O
zinc-coated	O
(	O
galvanized	O
)	O
nails	O
and	O
screws	O
.	O
</s>
<s>
Commercial	O
"	O
potato	B-Algorithm
clock	I-Algorithm
"	O
science	O
kits	O
include	O
electrodes	O
and	O
a	O
low-voltage	O
digital	O
clock	O
.	O
</s>
<s>
After	O
one	O
cell	O
is	O
assembled	O
,	O
a	O
multimeter	O
can	O
be	O
used	O
to	O
measure	O
the	O
voltage	O
or	O
the	O
electric	O
current	O
from	O
the	O
voltaic	O
cell	O
;	O
a	O
typical	O
voltage	O
is	O
0.9	O
V	O
with	O
lemons	B-Application
.	O
</s>
<s>
For	O
a	O
more	O
visible	O
effect	O
,	O
lemon	B-Application
cells	O
can	O
be	O
connected	O
in	O
series	O
to	O
power	O
an	O
LED	O
(	O
see	O
illustration	O
)	O
or	O
other	O
devices	O
.	O
</s>
<s>
Swartling	O
and	O
Morgan	O
have	O
published	O
a	O
list	O
of	O
low-voltage	O
devices	O
along	O
with	O
the	O
corresponding	O
number	O
of	O
lemon	B-Application
cells	O
that	O
were	O
needed	O
to	O
power	O
them	O
;	O
they	O
included	O
LEDs	O
,	O
piezoelectric	O
buzzers	O
,	O
and	O
small	O
digital	O
clocks	O
.	O
</s>
<s>
With	O
the	O
zinc/copper	O
electrodes	O
,	O
at	O
least	O
two	O
lemon	B-Application
cells	O
were	O
needed	O
for	O
any	O
of	O
these	O
devices	O
.	O
</s>
<s>
Substituting	O
a	O
magnesium	O
electrode	O
for	O
the	O
zinc	B-Application
electrode	O
makes	O
a	O
cell	O
with	O
a	O
larger	O
voltage	O
(	O
1.5	O
−	O
1.6	O
V	O
)	O
,	O
and	O
a	O
single	O
magnesium/copper	O
cell	O
will	O
power	O
some	O
devices	O
.	O
</s>
<s>
Note	O
that	O
incandescent	O
light	O
bulbs	O
from	O
flashlights	O
are	O
not	O
used	O
because	O
the	O
lemon	B-Algorithm
battery	I-Algorithm
is	O
not	O
designed	O
to	O
produce	O
enough	O
electric	O
current	O
to	O
light	O
them	O
.	O
</s>
<s>
By	O
multiplying	O
the	O
average	O
current	O
of	O
a	O
lemon	B-Application
(	O
0.001A/	O
1mA	O
)	O
by	O
the	O
average	O
(	O
lowest	O
)	O
voltage	O
(	O
potential	O
difference	O
)	O
of	O
a	O
lemon	B-Application
(	O
0.7V	O
)	O
we	O
can	O
conclude	O
that	O
it	O
would	O
take	O
more	O
than	O
6	O
million	O
lemons	B-Application
to	O
give	O
us	O
the	O
power	O
of	O
an	O
average	O
4320W	O
car	O
battery	O
.	O
</s>
<s>
The	O
acid	O
involved	O
in	O
citrus	O
fruits	O
(	O
lemons	B-Application
,	O
oranges	O
,	O
grapefruits	O
,	O
etc	O
.	O
)	O
</s>
<s>
Potatoes	O
have	O
phosphoric	O
acid	O
and	O
work	O
well	O
;	O
they	O
are	O
the	O
basis	O
for	O
commercial	O
"	O
potato	B-Algorithm
clock	I-Algorithm
"	O
kits	O
.	O
</s>
<s>
International	O
research	O
begun	O
in	O
2010	O
showed	O
that	O
boiling	O
potatoes	O
for	O
eight	O
minutes	O
improves	O
their	O
electrical	O
output	O
,	O
as	O
does	O
placing	O
slices	O
of	O
potatoes	O
between	O
multiple	O
copper	O
and	O
zinc	B-Application
plates	O
.	O
</s>
<s>
Zinc	B-Application
and	O
copper	O
electrodes	O
are	O
reasonably	O
safe	O
and	O
easy	O
to	O
obtain	O
.	O
</s>
<s>
Other	O
metals	O
such	O
as	O
lead	O
,	O
iron	O
,	O
magnesium	O
,	O
etc.	O
,	O
can	O
be	O
studied	O
as	O
well	O
;	O
they	O
yield	O
different	O
voltages	O
than	O
the	O
zinc/copper	O
pair	O
.	O
</s>
<s>
In	O
particular	O
,	O
magnesium/copper	O
electrodes	O
can	O
generate	O
voltages	O
as	O
large	O
as	O
1.6	O
V	O
in	O
lemon	B-Application
cells	O
.	O
</s>
<s>
This	O
voltage	O
is	O
larger	O
than	O
obtainable	O
using	O
zinc/copper	O
cells	O
.	O
</s>
<s>
The	O
fact	O
that	O
different	O
chemical	O
elements	O
such	O
as	O
copper	O
and	O
zinc	B-Application
are	O
used	O
can	O
be	O
placed	O
in	O
the	O
larger	O
context	O
that	O
the	O
elements	O
do	O
not	O
disappear	O
or	O
break	O
down	O
when	O
they	O
undergo	O
chemical	O
reactions	O
.	O
</s>
<s>
For	O
older	O
pupils	O
and	O
for	O
college	O
students	O
,	O
batteries	O
serve	O
to	O
illustrate	O
the	O
principles	O
of	O
oxidation-reduction	B-Operating_System
reactions	O
.	O
</s>
<s>
Students	O
can	O
discover	O
that	O
two	O
identical	O
electrodes	O
yield	O
no	O
voltage	O
and	O
that	O
different	O
pairs	O
of	O
metals	O
(	O
beyond	O
copper	O
and	O
zinc	B-Application
)	O
yield	O
different	O
voltages	O
.	O
</s>
<s>
Most	O
textbooks	O
present	O
the	O
following	O
model	O
for	O
the	O
chemical	O
reactions	O
of	O
a	O
lemon	B-Algorithm
battery	I-Algorithm
.	O
</s>
<s>
When	O
the	O
cell	O
is	O
providing	O
an	O
electric	O
current	O
through	O
an	O
external	O
circuit	O
,	O
the	O
metallic	O
zinc	B-Application
at	O
the	O
surface	O
of	O
the	O
zinc	B-Application
electrode	O
is	O
dissolving	O
into	O
the	O
solution	O
.	O
</s>
<s>
Zinc	B-Application
atoms	O
dissolve	O
into	O
the	O
liquid	O
electrolyte	O
as	O
electrically	O
charged	O
ions	O
(	O
Zn2+	O
)	O
,	O
leaving	O
2	O
negatively	O
charged	O
electrons	O
(	O
e−	O
)	O
behind	O
in	O
the	O
metal	O
:	O
</s>
<s>
This	O
reaction	O
is	O
called	O
oxidation	B-Operating_System
.	O
</s>
<s>
While	O
zinc	B-Application
is	O
entering	O
the	O
electrolyte	O
,	O
two	O
positively	O
charged	O
hydrogen	O
ions	O
(	O
H+	O
)	O
from	O
the	O
electrolyte	O
combine	O
with	O
two	O
electrons	O
at	O
the	O
copper	O
electrode	O
's	O
surface	O
and	O
form	O
an	O
uncharged	O
hydrogen	O
molecule	O
(	O
H2	O
)	O
:	O
</s>
<s>
The	O
electrons	O
used	O
in	O
the	O
copper	O
to	O
form	O
the	O
molecules	O
of	O
hydrogen	O
are	O
transferred	O
from	O
the	O
zinc	B-Application
through	O
an	O
external	O
wire	O
connecting	O
between	O
the	O
copper	O
and	O
the	O
zinc	B-Application
.	O
</s>
<s>
Goodisman	O
notes	O
that	O
numerous	O
recent	O
authors	O
propose	O
chemical	O
reactions	O
for	O
the	O
lemon	B-Algorithm
battery	I-Algorithm
that	O
involve	O
dissolution	O
of	O
the	O
copper	O
electrode	O
into	O
the	O
electrolyte	O
.	O
</s>
<s>
When	O
the	O
electrolyte	O
was	O
modified	O
by	O
adding	O
zinc	B-Application
sulfate	O
(	O
ZnSO4	O
)	O
,	O
the	O
voltage	O
from	O
the	O
cell	O
was	O
reduced	O
as	O
predicted	O
using	O
the	O
Nernst	O
equation	O
for	O
the	O
model	O
.	O
</s>
<s>
The	O
Nernst	O
equation	O
essentially	O
says	O
how	O
much	O
the	O
voltage	O
drops	O
as	O
more	O
zinc	B-Application
sulfate	O
is	O
added	O
.	O
</s>
<s>
When	O
the	O
battery	O
is	O
hooked	O
up	O
to	O
an	O
external	O
circuit	O
and	O
a	O
significant	O
electric	O
current	O
is	O
flowing	O
,	O
the	O
zinc	B-Application
electrode	O
loses	O
mass	O
,	O
as	O
predicted	O
by	O
the	O
zinc	B-Application
oxidation	B-Operating_System
reaction	O
above	O
.	O
</s>
<s>
The	O
Nernst	O
equation	O
prediction	O
failed	O
for	O
strongly	O
acid	O
electrolytes	O
(	O
pH	O
<	O
3.4	O
)	O
,	O
when	O
the	O
zinc	B-Application
electrode	O
dissolves	O
into	O
the	O
electrolyte	O
even	O
when	O
the	O
battery	O
is	O
not	O
providing	O
any	O
current	O
to	O
a	O
circuit	O
.	O
</s>
<s>
The	O
two	O
oxidation-reduction	B-Operating_System
reactions	O
listed	O
above	O
only	O
occur	O
when	O
electrical	O
charge	O
can	O
be	O
transported	O
through	O
the	O
external	O
circuit	O
.	O
</s>
<s>
The	O
additional	O
,	O
open-circuit	O
reaction	O
can	O
be	O
observed	O
by	O
the	O
formation	O
of	O
bubbles	O
at	O
the	O
zinc	B-Application
electrode	O
under	O
open-circuit	O
.	O
</s>
<s>
The	O
energy	O
comes	O
from	O
the	O
chemical	O
change	O
in	O
the	O
zinc	B-Application
when	O
it	O
dissolves	O
into	O
the	O
acid	O
.	O
</s>
<s>
The	O
energy	O
does	O
not	O
come	O
from	O
the	O
lemon	B-Application
or	O
potato	O
.	O
</s>
<s>
The	O
zinc	B-Application
is	O
oxidized	O
inside	O
the	O
lemon	B-Application
,	O
exchanging	O
some	O
of	O
its	O
electrons	O
with	O
the	O
acid	O
in	O
order	O
to	O
reach	O
a	O
lower	O
energy	O
state	O
,	O
and	O
the	O
energy	O
released	O
provides	O
the	O
power	O
.	O
</s>
<s>
In	O
current	O
practice	O
,	O
zinc	B-Application
is	O
produced	O
by	O
electrowinning	O
of	O
zinc	B-Application
sulfate	O
or	O
pyrometallurgical	O
reduction	O
of	O
zinc	B-Application
with	O
carbon	O
,	O
which	O
requires	O
an	O
energy	O
input	O
.	O
</s>
<s>
The	O
energy	O
produced	O
in	O
the	O
lemon	B-Algorithm
battery	I-Algorithm
comes	O
from	O
reversing	O
this	O
reaction	O
,	O
recovering	O
some	O
of	O
the	O
energy	O
input	O
during	O
the	O
zinc	B-Application
production	O
.	O
</s>
<s>
From	O
1840	O
to	O
the	O
late	O
19th	O
century	O
,	O
large	O
,	O
voltaic	O
cells	O
using	O
a	O
zinc	B-Application
electrode	O
and	O
a	O
sulfuric	O
acid	O
electrolyte	O
were	O
widely	O
used	O
in	O
the	O
printing	O
industry	O
.	O
</s>
<s>
While	O
copper	O
electrodes	O
like	O
those	O
in	O
lemon	B-Algorithm
batteries	I-Algorithm
were	O
sometimes	O
used	O
,	O
in	O
1840	O
Alfred	O
Smee	O
invented	O
a	O
refined	O
version	O
of	O
this	O
cell	O
that	O
used	O
silver	O
with	O
a	O
rough	O
platinum	B-Operating_System
coating	O
instead	O
of	O
a	O
copper	O
electrode	O
.	O
</s>
<s>
Unlike	O
the	O
zinc	B-Application
electrode	O
,	O
the	O
copper	O
or	O
platinized	O
silver	O
electrodes	O
are	O
not	O
consumed	O
by	O
using	O
the	O
battery	O
,	O
and	O
the	O
details	O
of	O
this	O
electrode	O
do	O
not	O
affect	O
the	O
cell	O
's	O
voltage	O
.	O
</s>
<s>
The	O
Smee	O
cell	O
used	O
amalgamated	O
zinc	B-Application
instead	O
of	O
pure	O
zinc	B-Application
;	O
the	O
surface	O
of	O
amalgamated	O
zinc	B-Application
has	O
been	O
treated	O
with	O
mercury	O
.	O
</s>
<s>
Apparently	O
amalgamated	O
zinc	B-Application
was	O
less	O
prone	O
to	O
degradation	O
by	O
an	O
acidic	O
solution	O
than	O
is	O
pure	O
zinc	B-Application
.	O
</s>
<s>
Amalgamated	O
zinc	B-Application
and	O
plain	O
zinc	B-Application
electrodes	O
give	O
essentially	O
the	O
same	O
voltage	O
when	O
the	O
zinc	B-Application
is	O
pure	O
.	O
</s>
<s>
With	O
the	O
imperfectly	O
refined	O
zinc	B-Application
in	O
19th	O
century	O
laboratories	O
they	O
typically	O
gave	O
different	O
voltages	O
.	O
</s>
<s>
In	O
the	O
video	O
game	O
Portal	B-Application
2	I-Application
,	O
the	O
antagonist	O
GLaDOS	O
is	O
embedded	O
into	O
a	O
potato-battery-run	O
computer	O
for	O
a	O
significant	O
part	O
of	O
the	O
game	O
.	O
</s>
<s>
In	O
the	O
episode	O
"	O
Lemons	B-Application
"	O
of	O
the	O
television	O
program	O
Red	O
Dwarf	O
(	O
tenth	O
series	O
(	O
Series	O
X	O
)	O
)	O
,	O
the	O
crew	O
travel	O
4,000	O
miles	O
from	O
Britain	O
to	O
India	O
in	O
23	O
AD	O
in	O
order	O
to	O
get	O
lemons	B-Application
to	O
build	O
a	O
lemon	B-Algorithm
battery	I-Algorithm
to	O
power	O
up	O
their	O
time	O
machine	O
's	O
returner	O
remote	O
.	O
</s>
<s>
In	O
NCIS	O
Season	O
7	O
episode	O
8	O
,	O
"	O
Power	O
Down	O
"	O
,	O
Abby	O
Sciuto	O
uses	O
lemons	B-Application
as	O
a	O
power	O
source	O
for	O
her	O
stereo	O
when	O
she	O
runs	O
out	O
of	O
batteries	O
during	O
a	O
blackout	O
.	O
</s>
<s>
In	O
Magnum	O
P.I.	O
,	O
Season	O
3	O
,	O
episode	O
2	O
,	O
"	O
Easy	O
Money	O
"	O
,	O
Magnum	O
uses	O
a	O
lemon	B-Algorithm
battery	I-Algorithm
to	O
charge	O
a	O
walkie-talkie	O
.	O
</s>
