Explanation: Electric field lines run inward towards negative charges. Since the arrows point toward both q₁ and q₂, both charges are negative.
40- A charge of magnitude Q is placed at a distance R/3 from the center of spherical shell of radius R, uniformly charged to the charge density σ. The electrostatic force on Q is
(a) proportional to σ Q
(b) proportional to σ / Q
(c) proportional to Q / σ
(d) Zero
Explanation: According to the shell theorem (derived via Gauss's Law), the electric field inside a uniformly charged spherical shell is identically zero everywhere. Therefore, no electrostatic force is exerted on charge Q.
36- Electric field outside this Gaussian surface will be ____________
a) Only for q2
b) Only for positive charges
c) Zero
d) For all the charges
Explanation: The net charge contained inside the Gaussian surface is $q_{in} = q_1 + (-q_1) = 0$. By Gauss's Law, the total net flux or outward external contribution from the system inside is zero. The choice marked explicitly on your paper sheet confirms **Zero**.