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1. Electric charges and fields — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics1. Electric charges and fields1 Mark
MCQ
If $\oint_s \vec{E} \cdot \overrightarrow{d S}=0$ over a surface, then:
  • A
    the electric field inside the surface is necessarily uniform.
  • ✓
    the number of flux lines entering the surface must be equal to the number of flux lines leaving it.
  • C
    the magnitude of electric field on the surface is constant.
  • D
    all the charges must necessarily be inside the surface.
✓

Answer

Correct option: B.
the number of flux lines entering the surface must be equal to the number of flux lines leaving it.
b
$\phi_{\text {closed }}=0$

$\text { So } \phi_{\text {in }}=\phi_{\text {out }}$

Number of field lines entering is equal number of field lines leaving.

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