Properties of Charges

Q. A conductor has $14.4\times {10}^{-19}$ coulombs positive charge. The conductor has (Charge on electron $1.6\times 10-19$coulombs )

1. 27 electrons in excess
2. 9 electrons in excess
3. 9 electrons in short
4. 27 electrons in short

Q.

What do you mean by quantization of electric charge?

Q.

One metallic sphere A is given a positive charge whereas another identical metallic sphere B of the exactly same mass as of A is given an equal amount of negative charge. Then

1. Mass of A and mass of B still remain equal
2. Mass of Bdecreases
3. Mass of Bincreases
4. Mass of A increases

Q.

A polythene piece rubbed with wool is found to have a negative charge of $3\times {10}^{–7}$ C. Estimate the number of electrons transferred (from which to which?) Is there a transfer of mass from wool to polythene?

Q.

Define mobility of electron

Q. A point charge $q_A=+100\mu \text{C}$ is placed at point $\text{A}(1,0,2)\text{m}$ and another point charge $q_B=+200\mu \text{C}$ is placed at point $\text{B}(4,4,2)\text{m}$. The magnitude of electrostatic force acting between them is:
(Take $k=9\times {10}^9\frac{{\text{N-m}}^2}{{\text{C}}^2}$ for calculation)

1. $10\text{N}$
2. $8.5\text{N}$
3. $7.2\text{N}$
4. $15\text{N}$

Q.

What are the four properties of electric charge?

Q. Two similar balls of mass ‘m’ are hung by a silk thread of length L and carry similar charges Q as in figure Assuming the separation to be small, the separation between the balls (denoted by x) is equal to

1. QLlmg
2. $\frac{QL}{mg}$
3. ${\left[\frac{Q^2.2L}{4\pi {ϵ}_0.mg}\right]}^{\frac{1}{3}}$
4. $\frac{Q^{2}L}{2\pi mg}$

Q. (a) Explain the meaning of the statement ‘electric charge of a bodyis quantised’. (b) Why can one ignore quantisation of electric charge when dealingwith macroscopic i.e., large scale charges?

Q.

How many electrons are there in one coulomb of electricity?

Q.

Explain the meaning of the statement 'electric charge of a body is quantized'.

Why can one ignore qunatization of electric charge when dealing with macroscopic, i.e., large scale charges?

Q.

SI unit of electric charge is:

Q. Which of the following electric field lines configuration is correct for an isolated positive point charge?
(Angles shown in the options are between the electric field lines and the tangent at the point of contact.)

1. 
2. 
3. 
4. 

Q. A finite line charge has $-Q$ uniformly distributed on upper half and $+Q$ uniformly distributed on lower half as shown.
Find the direction of electric field at point $\text{P}.$

1. Along positive $x-$ axis
2. Along ngative $x-$ axis
3. Along positive $y-$ axis
4. Along ngative $y-$ axis

Q. The figure shows a set of equipotential surfaces. There are a few points marked on them. An electron is being moved from one point to other. Which of the following statements is incorrect?

1. The electric field is directed along $+x-$ axis.
2. Work done by the electric field, in moving the electron from $\text{B}$ to $\text{C}$, is positive.
3. Work done by the electric field, in moving the electron from $\text{C}$ to $\text{D}$ is the same as from $\text{D}$ to $\text{E}$.
4. As the electron moves from $\text{E}$ to $\text{A}$, the potential energy increases

Q. A nucleus of mass $M$ emits $\gamma$-ray photon of frequency $\nu$. The loss of internal energy by the nucleus is :

Take $c$ as the speed of electromagnetic wave.

1. $0$
2. $h\nu$
3. $h\nu [1-\frac{h\nu }{2M{c}^2}]$
4. $h\nu [1+\frac{h\nu }{2M{c}^2}]$

Q.

Paper is an insulator. It gets attracted to the comp through charging by induction. How can this be possible when there are no free electrons on insulators and then how can electrons move and induced charges are formed?

Q. A conducting loop in the shape of a right angled isosceles triangle of height $10cm$ is kept such that the ${90}^{\circ }$ vertex is very close to an infinitely long conducting wire (see the figure). The wire is electrically insulated from the loop. The hypotenuse of the triangle is parallel to the wire. The current in the triangular loop is in counterclockwise direction and increased at a constant rate of $10A{s}^{-1}$. Which of the following statement(s) is (are) true?

1. The induced current in the wire is in opposite direction to the current along the hypotenuse
2. There is a repulsive force between the wire and the loop
3. The magnitude of induced emf in the wire is $\left(\frac{{\mu }_0}{\pi }\right)volt$
4. If the loop is rotated at a constant angular speed about the wire, an additional emf of $\left(\frac{{\mu }_0}{\pi }\right)volt$ is induced in the wire.

Q. A glass rod rubbed with silk is used to charge a gold leaf electroscope and the leaves are observed to diverge. The electroscope thus charged is exposed to X-rays for a short period. Then

1. The leaves will diverge further
2. The leaves will melt
3. The leaves will collapse
4. The divergence of leaves will not be affected

Q. "Analogous to the Coulomb's law the Newton's law of gravitation states that whenever two bodies of certain mass $m_1$ and $m_2$ are separated by distance ${}^{\prime }{r}^{\prime }$, then each of them attract each other by a force given as:
$F=\frac{G{m}_1{m}_2}{r^2}$
where ${}^{\prime }{G}^{\prime }$ is a constant"
Now, two point charges $+q_1$ and $+q_2$ are placed on a horizontal table such that gravitational attraction between them balances electrostatic repulsion. What can be concluded about nature of equilibrium position ?

1. It is a stable equilibrium position.
2. It is an unstable equilibrium position.
3. It is a neutral equilibrium position.
4. The data is not sufficient to arrive at conclusion.

Q. Two point charges are placed at separation $d$ in vacuum and the force between them is $F$. Now a dielectric slab of thickness $t=\frac{d}{3}$ and dielectric constant $K$ is placed between the charges and the force becomes $\frac{9F}{25}$. Find the value of $K$.

Q. If work done in moving a charge of 20 mC from infinity to a point O in an electric field is 15J, then what is the electric potential of this point.

Q.

The de Broglie wavelength of a proton and $\alpha$-particle are equal. The ratio of their velocities is:

1. $4:2$

2. $4:1$

3. $1:4$

4. $4:3$

Q.

In neon gas discharge tube 2.9*10^18 Ne+ ions move to the right through a cross section of the tube each second while 1.2*10^18 electrons move to the left this time. the electronic charge is 1.6*10^-19 coulomb. what is the net electric current in the tube?

Q.

Does a neutron have no net electric charge?

Q. Four particles each having a charge $q$ are placed on the four vertices of a regular pentagon. The distance of each corner from the centre is $a$. Find the electric field at the centre of the pentagon.

1. $\frac{kq}{a^2}$
2. $\frac{kq}{\sqrt{2}{a}^2}$
3. $\frac{kq}{2a^2}$
4. $\frac{kq}{\sqrt{3}{a}^2}$

Q. Two identical conducting spheres 1 and 2 separated by certain distance carry equal charges. They repel each other with a force F. Now a third identical conductor 3, initially uncharged is first brought in contact with 1, then 2 in turn, and is finally removed. What is the new force between 1 and 2?

1. F
2. 2F
3. $\frac{F}{2}$
4. $\frac{3}{8}F$

Q. Two identical rings $P$ and $Q$ of radius $0.1\text{m}$ are mounted coaxially at a distance $0.5\text{m}$ apart. The charges on the two rings are $2\mu C$ and $4\mu C$ respectively. The work done in transferring a charge of $5\mu C$ from the centre of $P$ to that of $Q$ is

1. $0.144\text{J}$
2. $1.28\text{J}$
3. $2.24\text{J}$
4. $0.72\text{J}$

Q. In a conducting hollow sphere of inner and outer radii $5\text{cm}$ and $10\text{cm}$, respectively, a point charge $1\text{C}$ is placed at point $A$, that is $3\text{cm}$ from the center $C$ of the hollow sphere. An external uniform electric field of magnitude $20\text{N/C}$ is also applied. Net electric force on this charge is $15\text{N}$, away from the center of the sphere as shown in the figure. Find the magnitude of net force exerted on the charge placed at point $A$ by the induced charges on the sphere.

1. $15\text{N}$
2. $20\text{N}$
3. $25\text{N}$
4. $35\text{N}$

Q. Identify the correct statement regarding an equipotential surface:

1. An equipotential surface and electric line of force never intersect each other.
2. An equipotential surface and electric line of force intersect at an angle of ${45}^{\circ }$.
3. An equipotential surface and electric line of force intersect at an angle of ${90}^{\circ }$.
4. An equipotential surface and electric line of force intersect at an angle of ${60}^{\circ }$.