Under what circumstances is the conservation of electric potential energy and kinetic energy used?

It should be the case that it is not subject to external forces, to be exact, except for the electric field force.

The electric field force is the internal force of the entire system.

The electric field force is used to do positive work, and the electric potential energy is replaced by kinetic energy;

The electric field force does negative work, and the kinetic energy is converted into electric potential energy.

If a moving object is considered as an object, the electric field force can be seen as an external force.

Therefore, when studying mechanics and physics, we must find the right object!

You have to analyze an object completely by analyzing it, and don't confuse anything else.

To analyze a system, analyze it.

It should be the case that only the electric field force does the work.

Because work is a measure of energy transformation, any change in energy corresponds to the work done by a force. Therefore, the change of kinetic energy must also be forceful in the work; And the change in electric potential energy also corresponds to the work done by the electric field force. In order for total energy to be conserved, one of the two energies must decrease and one increase, and be equal.

Of course, this force must be a force, and the work done by the same force cannot even be done by gravity.

Of course, for a charged body this force is an external force. In fact, the situation is similar with any force acting on it. Like the law of conservation of mechanical energy.

To correct a misconception on the second floor, it is not that other forces do work and are conserved as zero, that is just unchanged.

Only the electric field force does the work, or the total work done by other external forces is 0

There can be other external forces, as long as they do no work or the total work done is 0

Electromotive forceRelation to constant electric field: Electrode potential includes:Standard electrode potentialand gram-type measuring potential and fooling around. An electrode potential shield is a measured or calculated value when there is no current passing through the electrode and when the various reactions in the battery are in equilibrium.

They both belong to the equilibrium electrode potential value.

The constant electric field should refer to the electric field with a constant voltage, that is, the electric field that ensures that the voltage is basically constant, so a constant electric field can ensure that there is a basically constant voltage, that is, the electric potential is constant, so that the electrons can flow.

This is a basic condition for the flow of electrons, and electromotive force is a potential energy that exists between high and low voltage potentials due to the presence of voltage, that is, the energy that electrons will release when they flow from high potential to low potential, both of which are the causes of the flow of electrons, and they exist at the same time.

Piezoelectric electromotive force.

God touch crystal piezoelectric ignition, crystal microphone, etc.)** in mechanical work.

caused by polarization.

When dielectric. When the crystal is deformed by the action of an external force in a certain direction, it will cause the relative transfer of the positive and negative charge centers inside it and produce a polarization phenomenon, which will lead to the generation of opposite charges on the corresponding two surfaces, so that the voltage will be generated on the two surfaces, which is called piezoelectric electromotive force; When the external force is removed, the charge on the surface also disappears and returns to the uncharged state. When the direction of action of the external force changes, the polarity of the charge also changes.

The condition for the conservation of momentum is that the system is not subject to external forces or external forces.

Zero. To study the premise of conservation of momentum, it is necessary to clarify a system, that is, the conservation of momentum of the whole system.

There is no saying that kinetic energy is conserved, and kinetic energy should be conserved, which of course means that kinetic energy is not converted into other forms of energy, such as no friction, it will not be converted into thermal energy (or internal energy), and no electromagnetic induction will not be converted into electrical energy.

There is conservation of mechanical energy.

That is, only gravity or elastic force is used to do work, mechanical energy is conserved, and energy is conserved.

The problem is the same, that is, it is not converted into other forms of energy, and when gravity or elastic force does work, it is a conversion between mechanical energy, and the total amount of mechanical energy in the system is constant.

For a single object (particle), its kinetic energy is conserved if its net force is zero or the algebraic sum of the works done by each force is zero.

The question of judging whether to do work or not: the key is to look at the two necessary factors of merit, the first one is strength; The second is the displacement in the direction of the force. The so-called "displacement in the direction of the force" can be understood as follows: when the displacement is parallel to the force, then the displacement is the displacement of the position in the direction of the force.

When the displacement is perpendicular to the force, then the displacement is perpendicular to the force, then the displacement is not a displacement in the direction of the force; When the displacement is neither perpendicular nor parallel to the force, the displacement can be orthogonally decomposed, and its partial displacement parallel to the direction of the force is still called the displacement in the direction of the force.

The two equations for the conservation of momentum and the conservation of kinetic energy (mechanical energy) (which should be the equation of elastic positive collision) are:

ma*va0＝ma * va＋mb * vb。

ma*va0^2 / 2）＝（ma * va^2 / 2）＋（mb * vb^2 / 2）。

That is: ma*va0 type key-clear ma * va mb * vb

ma* va0^2

ma * va^2 ＋mb * vb^2

Deform Equation 1 to get ma*

va0－ va）＝mb * vb。

Deform Equation 2 to get the pre-bout ma*

va0^2－ va^2）＝mb * vb^2。

Since va0≠va , divide the above two equations to get.

va0＋ va＝

vb Through the above processing, the equation becomes a primary function.

It is easy to find by combining Equation 1 and Equation 3.

va＝（ma－mb）*

va0 /（ma＋mb）。

vb＝2* ma* va0 /（ma＋mb）。

Note: The above va0, va, vb are inclusive of directions (plus or minus).

But from a computational point of view, they can be related to each other by formulas. i.e.: momentum p=mv kinetic energy ek=1 2mv 2;p^2=m^2v^2=2m*1/2mv^2=2mek；The relationship between kinetic energy and momentum:

p^2=2mek。

Momentum and kinetic energy are two physical quantities of different natures that measure the motion of an object, respectively: bright plum.

Momentum is a measure of the motion of an object, which is measured by mechanical motion from the perspective of mechanical motion transmission. In the process of transmission of mechanical motion, the transmission of mechanical motion follows the law of conservation of momentum.

Energy is also a measure of the motion of an object. It measures mechanical motion in terms of its ability to transform into a certain amount of other forms of motion from the perspective of energy conversion. In the process of conversion of kinetic energy, the conversion of kinetic energy follows the law of transformation and conservation of energy.

1. The system is not subject to external forces.

2. The system is subjected to external forces, but the sum of external forces is zero.

3. The system is subject to external forces, but the internal forces are much greater than the external forces, such as collisions.

4. The system is subjected to an external force and the resultant external force is not zero, but the resultant external force in a certain direction is zero, then the momentum in that direction is conserved.

Law of Conservation of Momentum: A system is not subject to an external force or the resultant external force is zero, and the momentum of the system remains the same. i.e. δp1 = -δp2

Law of Conservation of Angular Momentum: For a particle, the angular momentum theorem can be expressed as: the microquotient of the angular momentum of a particle to a fixed point to time is equal to the moment of the force acting on the particle.

For a single object, the condition for conservation of kinetic energy is that the work done by the resultant external force is zero.

For one system, it's a fully elastic collision. and must be both pre-collision and post-collision.

In the process of interaction between objects, if there is no external force, then the total momentum of the interacting objects remains constant, which is the law of conservation of momentum. It is applicable to the condition that the interacting objects are not subject to external forces, and of course, there is no such thing as an object in the world that is not subject to external forces. There are three main situations in which the law of conservation of momentum is applied:

1) The resultant external force on the system is zero.

2) The external force on the system is much smaller than the interaction force (internal force). So much so that the influence of external forces can be ignored.

3) The system as a whole does not satisfy the law of conservation of momentum, but in a particular direction, the system is not subject to external forces, or the external forces are much smaller than the internal forces, then the partial momentum of the system along this direction is conserved.

Hope it helps.

Determination of the conditions for the law of conservation of momentum to be established.

<> According to the kinetic energy theorem, kinetic energy is related to the work done by the combined external force. Combined external force to do positive work, kinetic energy increases, and negative work kinetic energy decreases Electric potential energy is related to the work done by the electric field force, the electric field force does positive work, the electric potential energy decreases, the electric field force does negative work, and the electric potential energy increases. In the case where only the electric field force does the work, the electric potential energy and kinetic energy are conserved.

The electric potential energy decreases, and the electrostatic force does positive work, and the electric potential energy increases, and the electrostatic force does negative work. According to the kinetic energy theorem, the electrostatic force does positive work and the kinetic energy increases, and the electrostatic force does negative work and the kinetic energy decreases, that is, the electric potential energy decreases, the kinetic energy increases, the electric potential energy increases, and the kinetic energy decreases.

Kinetic energy is completely unrelated to the formula for calculating electric potential energy, but there is a conversion between kinetic energy and electric potential energy.

For example, a stationary charged ball moves in an electric field by the force of the electric field, which is the conversion of electric potential energy into kinetic energy.

If the charged ball moves in the opposite direction to the direction of the electric field force, it is the kinetic energy that is converted into electric potential energy.

The positive work done by the electric field force of w=qu=- ep is reduced by the electric potential energy, and the decrease in the electric potential energy is equal to the work done by the electric field force.

By the kinetic energy theorem wqu= ek the positive kinetic energy of the electric field force increases, and the negative work kinetic energy of the electric field force decreases.

The relationship between the potential energy and kinetic energy of an electric charge.

ek=-△ep