Question Bank For Unit 4 Revised
Question Bank For Unit 4 Revised
Question Bank For Unit 4 Revised
Objective questions
Q. 1. State Coulomb’s law in electrostatics with its mathematical form.
Q. 5. State and write the mathematical form of Faraday’s laws of electromagnetic induction.
law?
Q.2. Twelve equal charges, q are situated at the corners of a regular 12 sided polygon (for
instance one on each numeral of a clock face).
a) What is the net force on a test charge Q at the center?
b) Suppose one of the 12 ‘q’s is removed (the one at “6 o’ clock). What is the force on
Q? Explain your reasoning carefully. 𝑞𝑄
[Ans. a) 0, b) 𝐹 = , 𝑡𝑜𝑤𝑎𝑟𝑑𝑠 6 𝑜′𝑐𝑙𝑜𝑐𝑘.]
𝑟2
Q.3. Two point charges of 0.7mC and 4.9µC are situated in free space at (2,3,6) and (0,0,0).
Assume distances are in meter; calculate the force acting on the 0.7mC charge.
[Ans. 0.63 N]
Q.4. Four point charges each of 10µC are placed in free space at the points (1,0,0), (-1,0,0),
(0,1,0) and (0,-1,0) m respectively. Determine the force on a charge of 30µC located at a
point (0,0,1) m. [Ans. 3.8 N]
Q.5. Q1 and Q2 are the point charges located at (0,-4,3) and (0,1,1). If Q1 is 2 nC, Find Q2
such that the force on a test charge at (0, -3, 4) has no Z component. [Ans. -2.5nC]
Q. 6. Two small identical conducting spheres have charges of 2 nC and -1nC respectively.
1
When they are separated by 4 cm apart, find the magnitude of the force between them.
If they are brought into contact and then again separated by 4cm, find the force
2
between them. Also comment about the type of forces in each case.
[Ans. 11.2 x 10-6 N and 1.41 x 10-6 N]
Q. 7. Find the electric field (magnitude and direction) a distance z above the midpoint
between two equal charges, q, a distance d apart as shown in below figure. Check that your
result is consistent with what you would expect when z>>d.