When
work is done on an object to change its position, this work is stored
in the system (between particles that are bound by certain types of
forces) in the form of energy called potential energy.
Potential
Energy: The energy that an object possesses as a result of its
position or state.
Examples of Potential Energy:
1 -
Potential energy stored in a taut or compressed spring coil (elastic
potential energy):
Contraction or Elongation of a Spring Its
molecules gain a new position thus storing elastic potential energy.
Then the spring does work until it gets rid of this energy in order
to return to its resting position. The
more a spring is compressed or stretched away from its equilibrium
point, the greater the potential energy stored in the
system. The stretched or compressed spring has stored potential
energy
2 -
Potential energy stored in a taut rubber string (elastic potential
energy):
Elongation of a Rubber String: Its molecules gain a new
position and thus store elastic potential energy. Therefore, the taut
rubber string moves when the force acting on it is removed until it
gets rid of this energy in order to return to its resting position.
3 -
Potential energy stored in an object lifted from the Earth's surface
(gravitational potential energy):
Gravitational potential energy
is related to the position of objects relative to the Earth's surface
relative to the gravitational field.
4-
Potential energy stored in the electrons inside the battery(Chemical
potential energy):
Electrons move when the battery is connected
and the circuit is closed.
When a body of mass m is lifted
a vertical distance h above the surface of the Earth, the work done W
is determined from this equation: $${W=Fh}$$
where
F is the force needed to lift the body upwards against gravity and is
equal to its weight w:
The work done is stored inside the
body as potential energy:
*In the opposite figure, the
work done to lift a body of mass m from position A to position B
is:
$${W=mgh -
mgh
W=mg(h-h)=mg𝛥h
W=𝛥(PH)}$$
Life
Applications:
• When a box weighing 450N is lifted vertically upwards by a distance
of 1m
The work done is: $${W=wh=450×1=450J}$$
This requires a force
equal to the weight of the box: $${F=\frac{W}{d}=\frac{450}{1}=450N}$$
• And
when the same box is lifted vertically upwards by a distance of 1m
using an inclined plane of length 3m
The work done
is:$${W=wh=450×1=450J}$$
This
requires less force than the weight of the box, but it will require a
greater displacement: $${F=\frac{W}{d}=\frac{450}{3}=150N}$$
Potential energy is
stored within any system when an external force performs work against
the system's natural conservative force.
Examples:
When a ball is thrown
upward, work is done against the natural gravitational force (which
pulls objects toward the center of the Earth). Consequently, kinetic
energy is converted into potential energy stored within the
gravitational field (the system). The ball's initial kinetic energy
is gradually and completely transformed into potential energy stored
in the field at its maximum height. Thereafter, the field releases
this stored potential energy, converting it back into kinetic energy
so that the system returns to its lower-energy, most stable state.
When charging a Daniell
cell using an external power source, electrical work is performed
against the natural direction of the electrochemical reaction. The
external electromotive force forces electrons to flow opposite to
their spontaneous path—from the copper electrode to the zinc
electrode. Consequently, electrical energy is converted into chemical
potential energy stored within the electrochemical system: copper
atoms oxidize into ions dissolved in solution, while zinc ions gain
electrons and deposit as metallic atoms.
Simultaneously, ions within
the salt bridge are forced to migrate opposite to their natural
direction to maintain electrical neutrality in both solutions (anions
migrate toward the copper half-cell, while cations move toward the
zinc half-cell). Thus, the electrical energy from the external source
is gradually and completely transformed into chemical potential
energy stored in the cell at its maximum voltage or charge capacity.
Subsequently (during usage and discharge), the system releases this
stored chemical potential energy, converting it back into electrical
energy (electron movement and reverse ion flow in the salt bridge),
allowing the system to return to its lowest-energy, most stable
chemical state.
محاكاة خلية دانيال - طاقة الوضع والكهروكيمياء
⚡
محاكاة خلية دانيال التفاعلية
✨ المفهوم الفيزيائي المستهدف
طاقة الوضع تُخزن عند بذل شغل خارجي معاكس للقوة الطبيعية المحافظة
«طاقة الوضع تُخزن في أي نظام عندما تُبذل قوة أو طاقة خارجية (شغل) عكس اتجاه القوة الطبيعية المحافظة لهذا النظام.»
أثناء التفريغ، يحدث التفاعل التلقائي وتتحرر الطاقة. أثناء الشحن، نبذل شغلاً خارجياً لعكس التفاعل وإعادة تخزين الطاقة الكيميائية.
