Physics · 2015
JEE Main · 10 April 2015, Shift 1 · Q14
A thin disc of radius b =2 a has a concentric hole of radius 'a' in it (see figure). It carries uniform surface charge ' σ ' on it. If the electric…
A thin disc of radius $\displaystyle \mathrm{b}=2 \mathrm{a}$ has a concentric hole of radius 'a' in it (see figure). It carries uniform surface charge ' $\displaystyle \sigma$ ' on it. If the electric field on its axis at height 'h' (h<<a) from its centre is given as 'Ch' then value of ' $\displaystyle \mathrm{C}^{\prime}$ is :
Official answer
(3)
$\displaystyle \frac{\sigma}{4 \mathrm{a} \epsilon_0}$
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JEE Main 2015 Physics question, with the answer from NTA’s final answer key. Where our answers come from.