Question: Q. 5. In given figure, two positive charges $q_{2}$ and $q_{3}$ fixed along the $y$-axis, exert a net electric force in the $+x$ direction on a charge $q_{1}$ fixed along the $x$ axis. If a positive charge $Q$ is added at $(x, 0)$, the force on $q_{1}$
Very Short Answer Type Questions
(1 mark each)
Q. 1. A point charge $+Q$ is placed in the vicinity of a conducting surface. Draw the electric field lines between the surface and the charge.
R [O.D. Comptt. I, II, III 2017]
[CBSE Marking Scheme, 2017]
Q. 2. Why do the electrostatic field lines not form closed loops?
U] [O.D. I, II, III 2014]
Show Answer
Solution:
Ans. Electric field lines start from positive charge and end at infinity. Therefore, these lines do not form closed loops. [CBSE Marking Scheme, 2014] 1
(a)
(b) (a) shall increase along the positive $x$-axis.
(b) shall decrease along the positive $x$-axis.
(c) shall point along the negative $x$-axis.
(d) shall increase but the direction changes because of the intersection of $Q$ with $q_{2}$ and $q_{3}$.
[NCERT Exemp.]
Ans. Correct option:
Explanation: Net force on charge $q_{1}$, by other charges $q_{2}$ and $q_{3}$ is along the $+x$-direction, so nature offorces between $q_{1}$ and $q_{2}$ and $q_{1}$ and $q_{3}$ are attractive. This is possible when charge $q_{1}$ is negative. Now, if a positive charge $Q$ is placed at $(x, 0)$, then, the force on $q_{1}$ shall increase. Its direction will be along positive $x$-axis.
Commonly Made Error
- Some candidates do not understand about attraction and repulsion of net force. Here net force is the vector sum of all forces in $x$-direction.
