Question

a charge on a sphere of radius 2 cm is 2u c while charge on a sphere of radius 5cm is 5uc . find the ratio of electric fields at points 10cm from the centre of the sphere.
a.1:1,b.2:5,c.5:2,d.4:25​

Answer 1

b is the correct option for this a

Answer 2

The ratio of electric fields is 5 : 2 .

Given :

Charge on a sphere of radius 2 cm is 2 uC .

Charge on a sphere of radius 5 cm is 5 uC .

We need to find the ratio of electric fields at points 10 cm from the centre of the spheres.

The distance is outside the sphere .

We know electric field outside the sphere is given as :

$E=\dfrac{kq}{r^2}$

Therefore , their ratio is :

$\dfrac{E_1}{E_2}=\dfrac{\dfrac{kq_1}{r_1^2}}{\dfrac{kq_2}{r_2^2}}\\\\\\\dfrac{E_1}{E_2}=\dfrac{r_2^2}{r_1^2}\times \dfrac{q_1}{q_2}\\\\\dfrac{E_1}{E_2}=\dfrac{5^2}{2^2}\times \dfrac{2}{5}\\\\\dfrac{E_1}{E_2}=\dfrac{5}{2}$

Therefore , the ratio is 5 : 2 .

Hence , this is the required solution .

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Electrostatics

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