Electric Field due to Spherical Shell?

📌 CONCEPT: The electric field due to a spherical shell is zero at every point outside the shell, as per the properties of a spherical charge distribution.

📐 RULE / FORMULA: The electric field at the centre of a spherical shell is given by E = k * q / r^2, where q is the charge on the shell and r is the radius of the shell.

💡 WORKED EXAMPLE: For a spherical shell with radius 10 cm and charge 4 μC, the electric field at its centre would be E = (9 * 10^9 N m^2 C^-2) * (4 * 10^-6 C) / (0.1 m)^2, which simplifies to E = 0 N/C. This is because the test charge of -2 μC placed at the centre of the shell would experience no net electric field.

⚠️ COMMON MISTAKE: Students often fail to consider the properties of spherical charge distributions and incorrectly assume that the electric field at the centre of a spherical shell is non-zero.