COMEDK 2023 Evening Shift | Electrostatics Question 12 | Physics

A spherical metal ball of density '$$\rho$$' and radius '$$r$$' is immersed in a liquid of density '$$\sigma$$'. When an electric field is applied in the upward direction the metal ball remains just suspended in the liquid. Then the expression for the charge on the metal ball is :

$$q=\frac{\left[\frac{4}{3} \pi r^3 \rho g\right]}{\sigma E}$$

$$q=\frac{\left[4 \pi r^3(\rho-\sigma) g\right]}{3 E}$$

$$q=\frac{\left[4 \pi r^2 \rho g\right]}{\sigma E}$$

$$q=\frac{\left[4 \pi r^2(\rho-\sigma) g\right]}{E}$$

COMEDK 2023 Evening Shift

MCQ (Single Correct Answer)

-0

PQRS is square of side $$1 \mathrm{~m}$$. A charge of $$100 \mu \mathrm{C}$$ is placed at the centre of the square. Then the work done to take $$3 \mu \mathrm{C}$$ charge from the corner $$\mathrm{P}$$ to the corner $$\mathrm{R}$$.

$$9 \sqrt{2} \times 10^5 \mathrm{~J}$$

$$4.5 \times 10^5 \mathrm{~J}$$

Zero

$$1.8 \times 10^5 \mathrm{~J}$$

COMEDK 2023 Evening Shift

MCQ (Single Correct Answer)

-0

An electron and a proton having mass $$m_e$$ and $$m_p$$ respectively, initially at rest, move through the same distance '$$s$$' in a uniform electric field '$$E$$'. If the time taken by them to cover that distance is $$t_e$$ and $$t_p$$ respectively, then $$t_e / t_p$$ is equal to:

$$ \sqrt{\left(\frac{m_p}{m_e}\right)} $$

$$ \sqrt{\left(\frac{m_e}{m_p}\right)} $$

$$ \frac{\sqrt{\left(m_e\right)}}{m_p} $$

$$ \frac{m_e}{m_p} $$

COMEDK 2023 Evening Shift

MCQ (Single Correct Answer)

-0

The force between two electric point charges at rest in air is $$F_1$$ When the same arrangement is kept inside water, the force between them is $$F_2$$. Which of the following statement is correct?

$$F_2=0$$

$$F_2>F_1$$

$$F_2=F_1$$

$$F_2< F_1$$

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