Question

Hey Please answer this :(

Answer 1

Ahoy !

Good Question : ]

Hope my answer helps you

Answer 2

This is related to Gaussian theorem,
when,
electric field emitted by any charge or system of charge , directed outwards from the Gaussian surface , then charge must be positive .

here , electric field directed outward so, charge : positive .


we also know , that

dv = -E.dr

where dv is the element of potential
E is the electric field as function of r
dr is element of position .

now,

dv = -1000/r. dr

integrate both sides

(Vb - Va)= - 1000 [ lnr ] put limit rB = 0.4 to rA = 0.2

(Vb - Va) = -1000 [ln2] = -100 × 0.6931 V

= 693.1 Volt

I hope this will help you dear !!!!