(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Consider a semicircular piece of wire of length L and total charge of -Q where Q>0 (radius [itex]R=L/\pi[/itex]). What is the magnitude and direction of the electric field at the centre of the semi circle ?(if the wire was a full circle the centre would be the centre of the full circle).

2. Relevant equations

[tex]dE=k_{e}\frac{dq}{r^2}[/tex]

3. The attempt at a solution

I know what the direction of the electric field would be but not sure about the magnitude.

Say for example if the semi circle passes through the points (0,R), (-R,0) and (-R,0) on the x-y axis then the direction would be to the left. The bit I am unsure about what the magnitude of dq is?

I correctly guessed that it was

[tex]dq=2\lambda dx = 2\lambda R sin\theta d\theta[/tex]

where theta goes from 0 to Pi/2

but there is no way I can convince myself that is right. Can someone please explain WHY dq is that?

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# Homework Help: Electric field of semi circular piece of wire

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