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Capacitance, voltage and Potential difference

the capacity of parallel plate condenser is 5 micro Faraday. When a glass plate is placed between the plates of the conductor  its potential become 1/8th of the original value. The value of dielectric constant will be
(A)1.6
(B)5
(C)8
(D)40

 

Answer:

The charge remains same

Use Cm=KCo
and
V reduced to 1/8 means capacitance increased 8 times since Q=CV
So, the answer is evident

Potential

Devna asked.

find the potential at A ….a prson brings a mass of 1 kg from infinity to the pt A .initially the mass was at rest but it moves at a speed of 2 m/sas it reches A .the work done by person on mass is -3 J

Potential Difference

Pawan Asked

“What is meant by potential difference?”

Answer:

“Potential Difference between two points is the difference in Potential between the two points and is equal to the work done per unit charge ion carrying a positive test charge from one point to another against the electric field and without any acceleration”

de Broglie Wavelength

Alpha particle and a proton are accelerated from rest by the same potential. Find the ratio of their de- broglie wavelength

(Asked by Amritha)

 Answer:

Charge of alpha particle = 2e

Mass of alpha particle = 4 u

Charge of proton = e

mass of proton = u

The energy acquired by proton when accelerated through a pd of V,

E=eV

The momentum acquired by proton=

The de Broglie wavelength is given by 

Therefore, de Broglie wavelength of Proton,

Similarly,

Solution to HC Verma Problem

“Referring to HC Verma Part 2, chapter 29, Electric field and potential, Q 69
I think that Force is inversely proportional to square of the distance between the charged particles, so acceleration is not constant and hence
v*v  =  u*u  + 2*a*s   is not valid in this case.
How is proceed with this question ?” Satyam asked

Potential Difference – misconception

What actually it means when we say “potential difference across..” ? Does it indicate that the somehow the energy level of electrons across it is less than on the other side or is it just the amount of energy consumption across it. If latter is true then in AC we’ve voltages which dont algebraically add up together to give the applied voltage . reason stated is the phase difference. How can there be phases in something scalar like energy consumption ? (Posted by Thushar)

Answer: As per definition, “Potential difference is defined as the work done per unit charge in carrying a positive test charge between two points against the electric field.”

Just like water flows from a high altitude to low altitude, “current” flows from high positive potential to low positive potential. (And electrons flow in the reverse direction. Though electrons are the actually movable materials contained in a conductor, the direction of current was conventionally defined as the direction of motion of positive charges)

So, when there is a difference in potential the electrons will flow from lower “positive potential” (where the negative potential is high) to higher positive potential.

Phase refers to the angle of rotation corresponding to the present value of emf or current. One complete circle (or rotation) corresponds to 2(pi) phase. There is a difference between current and voltage refers to this.

In describing AC, we can imagine that the current and voltage in wave form is obtained by the projection of  rotating vectors, I0 and E0. The difference in angle between these which represents the waveform obtained for E and I correctly is known as the phase difference.

(I feel that this won’t suffice. Please as more questions to clarify your point; preferable as comments to the same post)


What is the mechanical energy of a bird on top of a moving Ship?

A bird is at rest on d top of a stick of moving ship….!! what is the mechanical energy that exists in the bird ???” – This question was posted by Fatima

Answer: The mechanical energy of the bird is both Potential and Kinetic as the bird is at a height with respect to ground and the bird is in motion along with the ship.

(Any deeper discussion is welcome)

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