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## Explain a method to create Uniform Electric Field.

The simplest method of creating a uniform electric field in a region is to keep two  equally charged thin plain metal sheets of opposite charge parallel to each other. As you can see from the derivation for electric field due to a plain sheet of charge, the electric field due to a plain sheet of charge is independent of distance (provided the distance is not large compared to the dimensions of the plain sheet of charge).

So, if you keep two plain metal sheets of same charge densities but opposite kind of charge, we get a fairly good uniform electric field in between the plates.

At regions close to a uniformly charged thin sheet also we get a uniform electric field, but as distance increases it may tend to become non uniform.

## Electricity field intensity within a conductor is always zero.Why?

Electricity field intensity within a conductor is always zero.Why?

The main difference between a conductor and an insulator is that the conductors contain plenty of free electrons which are free to move throughout the conductor; whereas the insulators do not have free electrons at room temperature.

When a conductor is held in an electric field, the free electrons inside them instantly drift opposite to the direction of electric field until the electric field due to the drift balances the external electric field and the net electric field inside the conductor becomes zero.

## Neutrons, Neutrons, Neutrons

I understand that  in large elements which contain many protons, there exist too many neutrons to extend the strength of strong nuclear force and to overcome the electromagnetic repulsion force of protons. Such elements are stable in this way. But, I read that element with too many neutrons are also unstable. WHY ?  What I know is that too many neutrons can’t enlarge the electromagnetic repulsion force and can increase the strong nuclear force, so they even make the nucleus more stable . What’s wrong with me ? Please!

## Electricity from ocean currents

How can we produce electricity using currents in ocean?

Electricty can be generated from ocean through various means, mainly

• Ocean Thermal Energy Devices
• Tidal Energy
• Energy of waves and
• Ocean Currents

The energy extraction from ocean currents is somewhat analogous to energy from winds. (ref http://www.boem.gov/Renewable-Energy-Program/Renewable-Energy-Guide/Ocean-Current-Energy.aspx)

Ocean current technology is still in its early stage of development.

For ocean current energy to be utilized successfully at a commercial scale, a number of engineering and technical challenges need to be addressed, including:

•  avoidance of cavitations (bubble formation);
•  prevention of marine growth buildup;
•  reliability (since maintenance costs are potentially high); and
•  corrosion resistance.

## Path dependence of Thermodynamic Variables

In NCERT TEXT BOOK it is written that
Since U is a state variable, ΔU depends only on the initial and final states and not on the path taken by the gas to go from one to the other. However, ΔQ and ΔW will, in general, depend on the path taken to go from the initial to final states. From the First Law of Thermodynamics,it is clear that the combination ΔQ – ΔW, is however, path independent.

ΔQ and ΔW will, in general, depend on the path taken ??andΔQ – ΔW, is however, path independent.
explain?? how??

## What is charge basically?

It may be rather silly but still I’m really curious to know about this.  What is charge basically?  I’m tired of reading and hearing charge is an inherent property of matter,  it is that which causes electric field etc.

First of all, I would like to tell that I am interested mainly in such questions which are branded silly. But many of those silly branded questions are not so silly.

Charge is defined in intermediate Physics as below

“Electric charge is the physical property of matter that causes it to experience a force when close to other electrically charged matter. “

The concept of electric field was introduced by Faraday to explain how two charges exert force on each other without physical contact. A charged particle (and also a time varying magnetic field) produces an electric field.

## Doubt on Alpha Rays

Alpha rays are helium nuclei since they have two protons and no electrons. They are He 2+ ions. However we have learnt that helium has highest ionization energy  and an extremely large amount of energy is needed for it to form an ion. According to this, it is not possible for a dipositive cation of helium to exist, however it does . What could be the reason?

First of all Alpha particle is not a doubly ionized Helium Atom. It is emitted from the nucleus of a discintegrating atom.

The energy required to peel off the two electrons is not too much as compared to the energy  involved in the alpha particle emission which is a nuclear reaction. Alpha particles are normally emitted as a part of radio active disintegrations, emitted by naturally unstable nuclei or artificially instabilized nuclei.

The ionization energy of helium is discussed in the purview  of the energy required to remove the electrons. Helium is having a stable duplet electronic configuration which makes it a stable atom. But the energy considerations in nuclear reactions are very much different and higher.

The first ionization energy of helium  is 2372.3 kJ/mol and the second ionization energy is 5250.5 kJ/mol

16 MeV = 16×1.6×10-13 J per nucleus 2.56 x 10-12 J per nucleus

which makes of the order of 1010 kJ per mol of Helium. This is evidently a huge amount compared to that of the ionization energy.

Basically there are a number of differences between chemical reactions and nuclear reactions.

1. In chemical reactions the electrons are taking part in reactions whereas in nuclear reactions the nucleons (protons and neutrons) are involved

2. In nuclear reactions the energy involved is very much large as compared to that in chemical reactions

3. The identity of the element dioes not change in chemical reactions whereas the identity is changed in most of the nuclear reactions.

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