Test Index

NCERT Class XII Chapter
Electric Charges and Fields
Questions With Solutions

© examsnet.com
Question : 12
Total: 34
(a) Two insulated charged copper spheres A and B have their centres separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is 6.5 × 10–7 C ? The radii of A and B are negligible compared to the distance of separation.
(b) What is the force of repulsion if each sphere is charged double the above amount, and the distance between them is halved?
Solution:  

(a) F =
1
4πε0
q1q2
r2
or F = 9 × 109
(6.5×10−7)2
(0.5)2
or F = 1.520 × 10−2 N
Electric Charges and Fields
(b) q1′ = 2q1 , q2′ = 2q2 and r' =
r
2
So , F' =
1
4πε0
q1′×q2′
(r′)2
 =
1
4πε0
2q1×2q2
(
r
2
)2
or F' = 16 × 1.520 × 10−2 = 24.32 × 10−2 N or F' = 0.24 N
© examsnet.com
Go to Question:
Prev Question
Next Question