KENDRIYA VIDYALAYA SANGATHAN, AHMEDABAD REGION CLUSTER LEVEL WORKSHOP AHMEDABAD-GANDHINAGAR CLUSTER DATE:12/12/2015 ELECTROSTATICS AND CURRENT ELECTRICTY Sr. Question and solutions Marks 1. Is the force acting between two point electric charges q1 and q2, kept at 1 some distance apart in air, attractive or repulsive, when (i) q1q2 > 0 (ii) q1q2 <0 ? Solution: (i) The force is repulsive. When > 0, it means that charges are q1q2 either both positive or both negative. This implies that the force between them is indeed repulsive. (ii) The force is attractive. When q1q2 < 0, it means that one of the charges is negative and the other is positive. This implies that the force between them is indeed attractive. Which orientation of an electric dipole in a uniform electric field would 2. 1 correspond to stable equilibrium? Solution: When the electric dipole is in the direction of the electric it is said to be in stable equilibrium. Figure three point charges +2q, and + 3q. Two charges + 2q and 3. 1 −q are enclosed within a surface What is the electric flux due to this −q ‘S’. configuration through the surface ‘S’? Solution: The net electric flux through the surface is, where is the permittivity of ‘S’ free space. 4. A wire of resistance 8R is bent in the form of a circle. What is the 1 effective resistance between the ends of a diameter AB? Solution: The effective resistance between the ends of diameter AB is. 5. A hollow metal sphere of radius 10 cm is charged such that the potential 1 on its surface is 5 V. What is the potential at the centre of the sphere? Solution:
KENDRIYA VIDYALAYA SANGATHAN, AHMEDABAD REGION CLUSTER LEVEL WORKSHOP AHMEDABAD-GANDHINAGAR CLUSTER DATE:12/12/2015 ELECTROSTATICS AND CURRENT ELECTRICTY Sr. Question and solutions Marks 1. Is the force acting between two point electric charges q1 and q2, kept at some distance apart in air, attractive or repulsive, when (i) q1q2 > 0 (ii) q1q2 <0 ? Solution: (i) The force is repulsive. When q1q2 > 0, it means that charges are either both positive or both negative. This implies that the force between them is indeed repulsive. (ii) The force is attractive. When q1q2 < 0, it means that one of the charges is negative and the other is positive. This implies that the force between them is indeed attractive. 1 2. Which orientation of an electric dipole in a uniform electric field would correspond to stable equilibrium? Solution: When the electric dipole is in the direction of the electric it is said to be in stable equilibrium. 1 3. Figure three point charges +2q, −q and + 3q. Two charges + 2q and −q are enclosed within a surface ‘S’. What is the electric flux due to this configuration through the surface ‘S’? Solution: The net electric flux through the surface ‘S’ is, where is the permittivity of free space. 1 4. A wire of resistance 8R is bent in the form of a circle. What is the effective resistance between the ends of a diameter AB? Solution: The effective resistance between the ends of diameter AB is. 1 5. A hollow metal sphere of radius 10 cm is charged such that the potential on its surface is 5 V. What is the potential at the centre of the sphere? Solution: 1
1185469794qbunit1&2.docx