A solid sphere made of insulating material has a radius R and has a total charge Q distributed uniformly in its volume. What is the magnitude of electric field intensity, E, at a distance r (o less than r less than R) inside the sphere

• A.  Q/(4 π εo r3).
• B.  3 Qr/(4 π εo R3).
• C.  Qr/(4 π εo R3).
• D.  QR/(4π εo r3).

Answer: (C)