Point Electrical Field

  • #1

Homework Statement

at a distance of 1.0 m from a point charge, the electric field is 40 J/C. What is the electric field at a distance of 2.0 m from the point charge?

The Attempt at a Solution

so, i understand that the elecric field should be = charge/distance(squared).

so I did:
40/(2^2) = 10 J/C

Is this correct or am i missing something? thanks
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  • #2
Are you sure it's J/c? Isn't that volts? Shouldn't it be N/c?

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/estatics/u8l4b3.gif [Broken]

The standard metric units on electric field strength arise from its definition. Since electric field is defined as a force per charge, its units would be force units divided by charge units. In this case, the standard metric units are Newton/Coulomb or N/C.

Excuse me if I'm blabbering, I'm just trying to look smart with my less than a year's worth of physics:biggrin:
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  • #3
im no craque at physics, but all my options are in J/C.
  • #4
[tex]k=\frac{1}{4\pi \epsilon}=9x10^9N[/tex]
Find q, and then use the above equations to find E at r=2.

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