Q. No.The amount of positive and negative charges in a cup of water (\(250\) g) are respectively:
| 1. | \(1.6 \times10^9\) C, \(1.4 \times10^9\) C |
| 2. | \(1.4 \times10^9\) C, \(1.6 \times10^9\) C |
| 3. | \(1.34 \times10^7\) C, \(1.34 \times10^7\) C |
| 4. | \(1.6 \times10^8\) C, \(1.6 \times10^7\) C |
If \(10^9\) electrons move out of a body to another body every second, how much time approximately is required to get a total charge of \(1\) C on the other body?
1. \(200\) years
2. \(100\) years
3. \(150\) years
4. \(250\) years
If a body is charged by rubbing it, its weight:
| 1. | remains precisely constant. |
| 2. | increases slightly. |
| 3. | decreases slightly. |
| 4. | may increase slightly or may decrease slightly. |
Given below are four statements:
| a. | The total charge of the universe is constant. |
| b. | The total positive charge of the universe is constant. |
| c. | The total negative charge of the universe is constant. |
| d. | The total number of charged particles in the universe is constant. |
Choose the correct option:
| 1. | (a) only |
| 2. | (b), (c) |
| 3. | (c), (d) |
| 4. | (a), (d) |
Two pith balls carrying equal charges are suspended from a common point by strings of equal length, the equilibrium separation between them is \(r\) (as shown in Fig. I). Now, as shown in Fig. II, the strings are rigidly clamped at half the height. The equilibrium separation between the balls now becomes:
1. \(\frac{r}{\sqrt[3]{2}}\)
2. \(\frac{r}{\sqrt[2]{2}}\)
3. \(\frac{2r}{3}\)
4. none of the above
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. \(1.6\times10^{39}\)
1. \(-Q/4\)
2. \(Q/4\)
3. \(-Q/2\)
4. \(Q/2\)
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. \(\frac{6}{4\pi \epsilon _{0}} \frac{Qq}{l^2}\)
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. \(\frac{3}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}\)
1. \(v\propto x\)
2. \(v\propto x^{-1/2}\)
3. \(v\propto x^{-1}\)
4. \(v\propto x^{1/2}\)
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