Question

i
V
A charge of + 7 uC is placed at the centre
of two concentric spheres with radius 2.0
cm and 4.0 cm respectively. The ratio of
the flux through them will be
A) 1:4 B) 1:2
li D) 1:16
​

Answer 1

(D) Right answer will be none of these.

Explanation:

As charge is placed at the center of both concentric spheres so, charge is surrounded by both spheres from all sides. Hence, whole flux will pass through both of the spheres in equal amount. As a result, the flux ratio will be 1:1. So, right answer is D.

Answer 2

Answer:

The ratio of  the flux through them will be 1:1.

(3) is correct option.

Explanation:

Given that,

Charge = +7μC

Radius of small sphere = 2.0 cm

Radius of large sphere = 4.0 cm

According to Gauss's law,

The total flux of electric field is equal to the charge divided by the permittivity.

In mathematically form,

$\phi=\dfrac{q}{\epsilon_{0}}$

We need to calculate the flux through small sphere and large sphere

Now, the flux for small sphere

$\phi_{s}=\dfrac{q}{\epsilon_{0}}$...(I)

The flux for large sphere

$\phi_{l}=\dfrac{q}{epsilon_{0}}$...(I)

We need to calculate the ratio of  the flux through them

Divided from equation (I) by (II)

$\dfrac{\phi_{s}}{\phi_{l}}=\dfrac{\dfrac{q}{\epsilon_{0}}}{\dfrac{q}{\epsilon_{0}}}$

$\dfrac{\phi_{s}}{\phi_{l}}=\dfrac{1}{1}$

Hence, The ratio of  the flux through them will be 1:1.