Point Charges (5 of 10) Work Done to Bring a Point Charge in From Infinity

Shows how to calculate the amount of work done to bring a charge a from infinity to close to another point charge.
An electric potential is the amount of work needed to move a unit of positive charge from a reference point to a specific point inside the field without producing an acceleration. It can also be stated as the amount of electric potential energy per unit of charge. The reference point is typically at infinity where the electric potential is assumed to be zero. The SI unit is joules per coulomb (J/C) or the volt (V).

The electric potential energy of a system of point charges is defined as the work required to bring the system of charges close together from an infinite distance. An object has electric potential energy by virtue of two key elements: its own electric charge and its relative position to another electrically charged objects. The SI unit for electric potential energy is the joules (J).

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[nedinnis]

Thank you! I wasn't listening to well in class when it was explained, this was a helpful recap.

[counterstrike]

Thankyou for helping me out! Better than my teachers!

[mikecondofit]

Currently in first year physics and you my friend are a gift from god

[coreymcmahon]

Thank you so much u have no idea how helpful this was

[duykhanh]

Does the electric energy stored in a point charge equal the work done to move it from initial position to infinity? If so how do I calculate it if there is no other charge?

[aesthetics]

thanks sir . I do have some questions related to this topic

[ppuckk]

Isn't Work = -ΔU (Negative Potential Energy)?

[thecomplexity]

I never understood how potential at final point can be given as kQq/rf and no one's ever had the patience to comprehend my point 😭

so I understand how kQq/rf corresponds to 'mgh' which is used when calculating potentials of earth-object system where h is the distance of the object from the ground (ground is considered to have 0 potential energy)

but mgh is only applied when we consider g to be constant over each point in the displacement h.. which it is not. With the change in displacement between the centres of the object and the earth, the g changes (g = GM/r² where G is gravitational constant, M is mass of the Earth and r is the displacement between the centre of the Earth and the centre of the object)

the change in g is not too significant for questions where a 2kg cat jumps down 10m and we are made to calculate the change in its potential energy..
but in questions like this, shouldn't the change in the force b/w the two bodies as the bodies move closer be taken into account? F = kQq/r^2 where Q is 18µC and q is 5µC and r is the distance between them. As the test charge q is brought closer to the stationary charge Q, shouldn't the F change owing to the change in r? This would make it so that using kQq/rf for the potential at final point would be inaccurate.

In theory, according to me, what should be done is the calculation of work on the test charge for very short distances from infinity such that for each short distance taken (which is a part of the total distance ri - rf), the force between the two charges is different (owing to the changed displacement b/w them) and the sum of all of these short distances is ri-rf

basically calculating the work done on q instantaneously for very very short distances as the force applied itself depends on distance b/w Q and q

[shqiponjebresa]

Hi! I've been trying to solve this problem for a long time and can't seem to solve it: What is the work done to bring a point charge( q= 2.0 * 10^-8 C) from infinity to a point 28cm from a spherical conductor surface(metalic) with a radius of 2.0cm . The sphere has a potential of 300V. It's supposed that the sphere is in void. I would really appreciate it if someone helped me.

[samuelcampbell]

What if the 5micro coulomb was move from a specific distance will d steps remain d same

[JRockTT]

Don't work and potential energy have opposite signs?

[MohamedGamal-rvcm]

What if the U is in negative sign ? what does it mean?

[taladiv]

Your voice bears some resemblance to Sal Khan.

[ironforged]

Something is wrong. Maybe my Module?
I tried the exact thing the video told me and got a result.
Then, I looked at the answer key to my module and the answer was the same answer this Video gave. Huh?