Electricity and magnetism confusion

In summary, the figures provided show the potential energy (U) at different distances from a point charge, and the student was trying to find E from the figures. However, they needed to know what data was given in order to solve the potential equation for Q and substitute it into the field equation. Once they had E, they could plot it on a graph.
  • #1
Dongorgon
20
0

Homework Statement


I've been set an assignment and I'm struggling with one question in particular:


Homework Equations



'Use the following data and plot the graphs for a point charge'

'Plot graph of E against r^2. Interpret the graph to describe electric field strength and electric potential.'

The figures provided are r(m)=Distance from a point charge, and, V(V)=Voltage at a distance 'r' from a point charge.

The Attempt at a Solution


More than anything I'm just really stuck how to find E from the figures provided? Any help would be greatly appreciated! Thanks
 
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  • #2
The filed at r=ri wil be:
E = -dV/dr ≈ -ΔVi/Δri
where ΔV = V(ri+1)-V(ri) and Δri = ri+1-ri
 
  • #3
I don't see how it would be possible to answer this without knowing what data you are given!
 
  • #4
Apologies, the date given is as follows:

R(m)=Distance from point charge:

0.0254
0.0508
0.05762
0.1016
0.127
0.1524
0.1778

And corresponding respectively, the V(V)=VOltage at a distance 'r' from a point charge:

236.22
214.57
157.58
108.03
94.48
85.3
73.11
 
  • #5
You're told that the given data corresponds to potential U at distances r from a point charge. What expressions do you know that correspond to electric potential U and electric field E at distance r from a point charge?
 
  • #6
Ok, so from equations to give V and E, I've come up with this as a potential solution for the first E value from the first two values of distance and voltage. Is this correct?
E_equation.png
 
  • #7
No need to plug in numerical values yet; you have a whole table full of values to plot later. Just write the expressions for potential and electric field for a point charge. Solve the potential expression for Q and substitute it into the field expression. That'll leave you with an expression for E involving only V and r. You can plot that since you have a table full of values for V and r.

(as an aside, note that electric field strengths are given in V/m or N/C, not Teslas which are a measure of magnetic field strength)
 
  • #8
Brilliant, piece of cake. Many thanks to those who have helped!
 

FAQ: Electricity and magnetism confusion

1. What is the difference between electricity and magnetism?

Electricity and magnetism are two different forces, but they are closely related. Electricity is the flow of charged particles, while magnetism is the force exerted by moving charged particles. In other words, electricity involves the movement of charges, while magnetism involves the interaction of charges.

2. How do electricity and magnetism work together?

Electricity and magnetism are closely related because electric currents create magnetic fields, and changing magnetic fields can induce electric currents. This is known as electromagnetism and is the basis for many technological applications, such as generators and electric motors.

3. Why do some materials conduct electricity and others do not?

Some materials, such as metals, have free electrons that can easily move and carry electric charges. These materials are known as conductors. Other materials, such as rubber or plastic, do not have free electrons and do not allow for the flow of electricity. These materials are known as insulators.

4. How do magnets work?

Magnets have two poles, north and south, which attract or repel each other depending on their orientation. This is due to the alignment of the microscopic magnetic domains within the magnet. When these domains are aligned, the magnet has a strong magnetic field. Magnets also have the ability to attract certain materials, such as iron, due to the alignment of their domains.

5. What is the relationship between electricity and energy?

Electricity is a form of energy that can be converted into other forms, such as light, heat, or mechanical energy. When a current flows through a wire, it transfers energy to the wire, which can then be used for various purposes. In turn, electricity can be generated from other forms of energy, such as chemical or mechanical energy.

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