When the electric flux associated with closed surface becomes positive, zero or negative ?
When the electric flux associated with closed surface becomes positive, zero or negative ?
If electric flux associated with area $\overrightarrow{\mathrm{S}}$ due to electric field $E$ is $\phi$, then
$\phi=\overrightarrow{\mathrm{E}} \cdot \overrightarrow{\mathrm{S}}$ $\therefore \phi=\mathrm{EScos} \theta$ $\text { where } \theta \text { is angle between } \overrightarrow{\mathrm{E}} \text { and } \overrightarrow{\mathrm{S}}$ $\text { (i) } \quad \text { If } \overrightarrow{\mathrm{S}} \perp \overrightarrow{\mathrm{E}} \text { means surface is parallel to } \overrightarrow{\mathrm{E}} \text { then, }\theta=90^{\circ}$ $\therefore\text { From equation (1), }$ $\phi=\text { EScos0 }^{\circ}=0$ $\therefore\text{ Flux associated with surface is zero.}$
$(ii)$ If $\theta<90^{\circ}$, then $\cos \theta>0$ (positive) hence flux is positive.
$(iii)$ If $\theta>90^{\circ}$, then $\cos \theta<0$ (negative) hence flux is negative.
All three are shown in figure $(a)$, $(b)$ and $(c) $ respectively.
Similar Questions
Is electric flux scalar or vector ?
Is electric flux scalar or vector ?
The given figure gives electric lines of force due to two charges $q_1$ and $q_2$. What are the signs of the two charges?
The given figure gives electric lines of force due to two charges $q_1$ and $q_2$. What are the signs of the two charges?
- [AIPMT 1994]
Given below are two statements:
Statement $I :$ An electric dipole is placed at the centre of a hollow sphere. The flux of electric field through the sphere is zero but the electric field is not zero anywhere in the sphere.
Statement $II :$ If $R$ is the radius of a solid metallic sphere and $Q$ be the total charge on it. The electric field at any point on the spherical surface of radius $r ( < R )$ is zero but the electric flux passing through this closed spherical surface of radius $r$ is not zero.
In the light of the above statements, choose the correct answer from the options given below:
Given below are two statements:
Statement $I :$ An electric dipole is placed at the centre of a hollow sphere. The flux of electric field through the sphere is zero but the electric field is not zero anywhere in the sphere.
Statement $II :$ If $R$ is the radius of a solid metallic sphere and $Q$ be the total charge on it. The electric field at any point on the spherical surface of radius $r ( < R )$ is zero but the electric flux passing through this closed spherical surface of radius $r$ is not zero.
In the light of the above statements, choose the correct answer from the options given below:
- [JEE MAIN 2021]
The wrong statement about electric lines of force is
The wrong statement about electric lines of force is
A cone of base radius $R$ and height $h$ is located in a uniform electric field $\vec E$ parallel to its base. The electric flux entering the cone is
A cone of base radius $R$ and height $h$ is located in a uniform electric field $\vec E$ parallel to its base. The electric flux entering the cone is
- [JEE MAIN 2014]