Electrostatic P.E. vs Gravitational P.E.

In summary, the conversation discusses two questions related to finding the energy needed for certain scenarios. The first question involves finding the energy needed to disassemble a planet with uniformly distributed mass, while the second question involves finding the potential energy of a metal sphere with a given charge. The solution for the first question involves considering the planet as concentric spherical shells, while the solution for the second question involves considering the charge to be concentrated on the sphere's surface.
  • #1
zorro
1,384
0

Homework Statement



I am confused b/w two questions:

1) The mass M of a planet Earth is uniformly distributed over a spherical volume of radius R. Find and expression for the energy needed to disassemble the planet against the gravitational pull amongst its constituent particles.

2) A metal sphere of Radius R has a charge Q. Find its potential energy.

The Attempt at a Solution



In both the cases, we have to find the work done in building the whole setup of radius R.

1) The spherical volume may be supposed to be formed by a large number of their concentric spherical shells. Let's consider that there is a core of radius x at any time. The energy needed to disassemble a spherical shell of thickness dx is

dW= Gm1m2/x

On solving and integrating, we get
W = 3GM2/5R

If I proceed analogously for 2), I get W = 3KQ2/5R which is not correct (unlike 1st)
Where is the error?
 
Physics news on Phys.org
  • #2
In the planet the mass is uniformly distributed throughout the volume. For a metallic conductor, all the charge is concentrated on the surface.
 
  • #3
That was quick!
Yeah you are right...I missed that.
Its much more easier to calculate in the case of E.P.E.

Thanks!
 

FAQ: Electrostatic P.E. vs Gravitational P.E.

What is Electrostatic Potential Energy?

Electrostatic Potential Energy (EPE) is the energy stored in an object due to its position in an electric field. It is the amount of work required to move a charged object from one point to another in an electric field.

What is Gravitational Potential Energy?

Gravitational Potential Energy (GPE) is the energy an object possesses due to its position in a gravitational field. It is the amount of work required to move an object from one point to another in a gravitational field.

How are Electrostatic P.E. and Gravitational P.E. similar?

Both Electrostatic P.E. and Gravitational P.E. are forms of potential energy that are dependent on an object's position. They both involve the concept of work and can be represented by the same equation: P.E. = mgh.

How are Electrostatic P.E. and Gravitational P.E. different?

The main difference between Electrostatic P.E. and Gravitational P.E. is the type of field that they are dependent on. EPE is dependent on an electric field, while GPE is dependent on a gravitational field. Additionally, the magnitude of the forces involved in each type of potential energy differ, with electric forces being much stronger than gravitational forces.

In what situations is Electrostatic P.E. more relevant than Gravitational P.E.?

Electrostatic P.E. is more relevant than Gravitational P.E. in situations involving charged particles and electric fields. This can include situations such as electric circuits, capacitors, and electric motors. Gravitational P.E. is more relevant in situations involving large objects and their interactions with the Earth's gravitational field, such as throwing a ball or launching a rocket.

Similar threads

Minimizing the Energy of Two Conductors Very Far Apart
Replies
23
Views
853
Electrostatic Potential Energy stored outside a shell.
Replies
1
Views
4K
Calculating Tidal Range (Gravitation)
Replies
12
Views
2K
What are the speeds of two Jupiter sized planets when they collide?
Replies
5
Views
1K
Energy stored in an electrostatic system
Replies
1
Views
1K
Electrostatic Potential Energy of a Sphere/Shell of Charge
Replies
2
Views
2K
Electrostatic Energy of Sphere in Shell
Replies
1
Views
2K
Finding the total gravitational potential energy of a gas cloud
Replies
1
Views
6K
Find the total electrostatic energy stored in the configuration
Replies
6
Views
2K
Sphere enclosed in shell is expanded, find work done
Replies
4
Views
2K

Hot Threads

Recent Insights

Back
Top