The ratio of the magnitude of electric force to the magnitude of gravitational force for an electron and a proton will be: ($$m_p=1.67\times10^{-27}~\mathrm{kg}$$$$m_e=9.11\times10^{-31}~\mathrm{kg}$$)
1. $$2.4\times10^{39}$$
2. $$2.6\times10^{36}$$
3. $$1.4\times10^{36}$$
4. $$1.6\times10^{39}$$

Subtopic:  Coulomb's Law |
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A charged metallic sphere A is suspended by a nylon thread. Another identical charged metallic sphere B held by an insulating handle is brought close to A such that the distance between their centres is 10 cm, as shown in Fig.(a). The resulting repulsion of A is noted. Then spheres A and B are touched by identical uncharged spheres C and D respectively, as shown in Fig.(b). C and D are then removed and B is brought closer to A to a distance of 5.0 cm between their centres, as shown in Fig. (c). What is the expected repulsion on A on the basis of Coulomb’s law?

1. Electrostatic force on A due to B remains unaltered.

2. Electrostatic force on A due to B becomes double.

3. Electrostatic force on A due to B becomes half.

4. Can't say.

Subtopic:  Coulomb's Law |
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Consider three charges $$q_1,~q_2,~q_3$$ each equal to $$q$$ at the vertices of an equilateral triangle of side $$l.$$ What is the force on a charge $$Q$$ (with the same sign as $$q$$) placed at the centroid of the triangle, as shown in the figure?

1. $$\frac{3}{4\pi \epsilon _{0}} \frac{Qq}{l^2}$$
2. $$\frac{9}{4\pi \epsilon _{0}} \frac{Qq}{l^2}$$
3. zero
4. $$\frac{6}{4\pi \epsilon _{0}} \frac{Qq}{l^2}$$

Subtopic:  Coulomb's Law |
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Consider the charges $$q,~q,$$ and $$-q$$ placed at the vertices of an equilateral triangle, as shown in the figure. Then the sum of the forces on the three charges is:

1. $$\frac{1}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}$$
2. zero
3. $$\frac{2}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}$$
4. $$\frac{3}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}$$



Subtopic:  Coulomb's Law |
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The accelerations of electron and proton due to the electrical force of their mutual attraction when they are 1 Å (=) apart are respectively: ($$m_p=1.67\times10^{-27}~\text{kg},~m_e=9.11\times10^{-31}~\text{kg}$$)
 1 $$2.5\times10^{22}$$ m/s2, $$2.5\times10^{22}$$ m/s2 2 $$2.5\times10^{22}$$ m/s2, $$1.4\times10^{19}$$ m/s2 3 $$1.4\times10^{19}$$ m/s2, $$2.5\times10^{22}$$ m/s2 4 $$1.4\times10^{19}$$ m/s2, $$1.4\times10^{19}$$ m/s2