Three charges are placed at the vertices of an equilateral triangle of side ‘a’ as shown in the following figure. The force experienced by the charge placed at the vertex A in a direction normal to BC is  (1) ${Q}^{2}/\left(4\pi {\epsilon }_{0}{a}^{2}\right)$ (2) $-{Q}^{2}/\left(4\pi {\epsilon }_{0}{a}^{2}\right)$ (3) Zero (4) ${Q}^{2}/\left(2\pi {\epsilon }_{0}{a}^{2}\right)$

Subtopic:  Coulomb's Law |
62%
From NCERT
AIIMS - 2003
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Two particles of equal mass $$m$$ and charge $$q$$ are placed at a distance of $$16~\text{cm}$$. They do not experience any net force. The value of $$\frac{q}{m}$$ is:
1. $$l$$
2. $$\sqrt{\frac{\pi \varepsilon_0}{G}}$$
3. $$\sqrt{\frac{G}{4\pi \varepsilon_0}}$$
4. $$\sqrt{4\pi \varepsilon_0 G}$$

Subtopic:  Coulomb's Law |
72%
From NCERT
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An electron is moving around the nucleus of a hydrogen atom in a circular orbit of radius r. The Coulomb force $\stackrel{\to }{F}$ on electron is (Where $K=\frac{1}{4\pi {\epsilon }_{0}}$)

(1) $-K\frac{{e}^{2}}{{r}^{3}}\stackrel{^}{r}$

(2) $K\frac{{e}^{2}}{{r}^{3}}\stackrel{\to }{r}$

(3) $-K\frac{{e}^{2}}{{r}^{3}}\stackrel{\to }{r}$

(4) $K\frac{{e}^{2}}{{r}^{2}}\stackrel{^}{r}$

Subtopic:  Coulomb's Law |
52%
From NCERT
PMT - 2003
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Five balls numbered 1 to 5 are suspended using separate threads. Pairs (1, 2), (2, 4), and (4, 1) show electrostatic attraction, while pairs (2, 3) and (4, 5) show repulsion. Therefore ball 1 must be:

1. positively charged.

2. negatively charged.

3. neutral.

Subtopic:  Coulomb's Law |
68%
From NCERT
PMT - 2003
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Equal charges q are placed at the four corners A, B, C, D of a square of length a. The magnitude of the force on the charge at B will be

(1) $\frac{3{q}^{2}}{4\pi {\epsilon }_{0}{a}^{2}}$

(2) $\frac{4{q}^{2}}{4\pi {\epsilon }_{0}{a}^{2}}$

(3) $\left(\frac{1+2\sqrt{2}}{2}\right)\frac{{q}^{2}}{4\pi {\epsilon }_{0}{a}^{2}}$

(4) $\left(2+\frac{1}{\sqrt{2}}\right)\frac{{q}^{2}}{4\pi {\epsilon }_{0}{a}^{2}}$

Subtopic:  Coulomb's Law |
69%
From NCERT
PMT - 1994
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Two identical conductors of copper and aluminium are placed in an identical electric field. The magnitude of induced charge in the aluminum will be

(1) Zero

(2) Greater than in copper

(3) Equal to that in copper

(4) Less than in copper

Subtopic:  Electric Field |
From NCERT
AIIMS - 1999
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Two spherical conductors $$B$$ and $$C$$ having equal radii and carrying equal charges in them repel each other with a force $$F$$ when kept apart at some distance. A third spherical conductor having same radius as that of $$B$$ but uncharged is brought in contact with $$B$$, then brought in contact with $$C$$ and finally removed away from both. The new force of repulsion between $$B$$ and $$C$$ is:
1. $$\frac{F}{4}$$
2. $$3\frac{F}{4}$$
3. $$\frac{F}{8}$$
4. $$3\frac{F}{8}$$

Subtopic:  Coulomb's Law |
61%
From NCERT
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Two equally charged, identical metal spheres A and B repel each other with a force 'F'. The spheres are kept fixed with a distance 'r' between them. A third identical, but uncharged sphere C is brought in contact with A and then placed at the mid-point of the line joining A and B. The magnitude of the net electric force on C is

(1) F

(2) 3F/4

(3) F/2

(4) F/4

Subtopic:  Electric Field |
55%
From NCERT
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An infinite number of charges, each of charge $$1$$ μC, are placed on the $$x$$-axis with co-ordinates $$x$$ = 1, 2, 4, 8, ....∞. If a charge of $$1$$ C is kept at the origin, then what is the net force acting on $$1~\text{C}$$ charge?
 1 $$9000$$ N 2 $$12000$$ N 3 $$24000$$ N 4 $$36000$$ N
Subtopic:  Coulomb's Law |
66%
From NCERT
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A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium, if q is equal to

(1) $-\frac{Q}{2}$

(2) $-\frac{Q}{4}$

(3) $+\frac{Q}{4}$

(4) $+\frac{Q}{2}$

Subtopic:  Coulomb's Law |
67%
From NCERT
PMT - 1995
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