How to Visualize Electric Fields

Q.

Write the properties of electric lines of force.

Q.

Two point charges 2 μC and 8μC are placed 12 cm apart. The position of point from 2 μC charge, where the electric field intensity is zero is:

1. 12 cm

2. 4 cm

3. 2 cm

4. 8 cm

Q.

Electric lines of force never intersect each other because

1. Lines of force always repel each other

2. Lines of force always attract each other

3. Point of intersection signifies two direction of electric field

4. From the point of intersection four tangent can be drawn which signifies four direction of field

Q. A ring of radius $R$ having a linear charge density $\lambda$ moves towards a solid imaginary sphere of radius $\frac{R}{2}$, so that the centre of the ring passes through the centre of sphere. The axis of the ring is perpendicular to the line joining the centres of the ring and the sphere. The maximum flux through the sphere in this process is

1. $\frac{\lambda R}{{\epsilon }_0}$
2. $\frac{\lambda R}{2{\epsilon }_0}$
3. $\frac{\lambda \pi R}{4{\epsilon }_0}$
4. $\frac{\lambda \pi R}{3{\epsilon }_0}$

Q. A charge of $1\text{C}$ is located at the centre of a sphere of radius $10\text{cm}$ whose centre coincides with that of a cube of side $20\text{cm}$. The ratio of the outgoing flux from the sphere to the outgoing flux from the cube will be

1. more than one
2. less than one
3. one
4. nothing can be said

Q. Three equal charges $+q$ each, are placed at the three vertices of an equilateral triangle centred at the origin. They are held in equilibrium by a restoring force of magnitude $F\left(r\right)=k{r}^2$ (where $k$ is a constant, $r$ is position of charge from origin) directed towards the origin. The distance of the any charge from the origin is ${\left(\frac{\sqrt{3}{q}^2}{p\pi {ϵ}_{0}k}\right)}^{\frac{1}{4}}$ where $p=$

Q.

A point charge causes an electric flux of −1.0 × 10³ Nm²/C to pass through a spherical Gaussian surface of 10.0 cm radius centered on the charge. (a) If the radius of the Gaussian surface were doubled, how much flux would pass through the surface? (b) What is the value of the point charge?

Q. A thin metallic spherical shell contains a charge $Q$ on its surface. A point charge $q_1$ is placed at the centre of the shell and another charge $q_2$ is placed outside the shell. All the three charges are positive. Then, the force on charge $q_1$ is

1. Towards right
2. Towards left
3. Zero
4. None of these

Q.

ABC is an equilateral triangle. Charges +q are placed at each corner. The electric intensity at O will be

Q. Calculate the electric field intensity E which would be just sufficient to balance the weight of an electron.If this electric field is produced by a second electron located below the first one what would be thedistance between them? \lbrack Given : e-1.6 x 1019 C, m, -9.1x 10-31 kg and g-9.8 m/s4

Q.

Write four properties of lines of force.

Q. A beam of electron passes, un-deflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons moves

1. in a circular orbit
2. along a parabolic path
3. along a straight line
4. in an elliptical orbit.

Q. (i) Use Gauss's law to find the electric field due to a uniformly charged infinite plane sheet. What is the direction of field for positive and negative charge densities ?
(ii) Find the ratio of the potential differences that must be applied across the parallel and series combination of two capacitors $C_1$ and $C_2$ with their capacitances in the ratio 1: 2 so that the energy stored in the two cases becomes the same.

Q. The electric field inside a spherical shell of uniform surface charge density is

1. Zero
2. Constant, less than zero
3. Directly proportional to the distance from the centre
4. None of the above

Q. Electric lines of force about negative point charge are:

1. Circular, anticlockwise
2. Circular, clockwise
3. Radial, inward
4. Radial, outward

Q. Three positive charges of equal value q are placed at the vertices of an equilateral triangle. The resulting lines of force should be sketched as in

1. 
2. 
3. 
4. 

Q.

Can a body have a charge a) 0.32X10^-18C

b)0.64X10^-20C

c)4.8X10^-21C

Please explain in detail with a solution

Q. Apply Gauss law to show that for a charged spherical shell the electric field outside the shell is as if the entire charge were concentrated at the centr

Q. The wrong statement about electric lines of force is

1. They do not intersect each other at a point
2. They have the same form for a point charge and a sphere
3. They have physical existence
4. These originate from positive charge and end on negative charge

Q. Find out the magnitude of electric field intensity at point $(2,0,0)$ due to a dipole of dipole moment $\overrightarrow{P}=\hat{i}+\sqrt{3}\hat{j}$ kept at origin. Also find the potential at that point.

1. $\left|E\right|=\frac{K}{8},V=\frac{K}{2}$
2. $\left|E\right|=\frac{K}{2\sqrt{2}},V=\frac{7K}{8}$
3. $\left|E\right|=\frac{\sqrt{7}K}{8},V=\frac{K}{4}$
4. $\left|E\right|=\frac{K}{2},V=\frac{K}{4}$

Q. Assertion : Electric lines of force cross each other.
Reason : Electric field at a point superimpose to give one resultant electric field.

1. If the assertion and reason both are false.
2. If assertion is false but reason is true.
3. If both assertion and reason are true but reason is not the correct explanation of the assertion.
4. If assertion is true but reason is false.
5. If both assertion and reason are true and the reason is the correct explanation of the assertion.

Q.

Why do electric lines of force never intersect each other?

Q. A charge $q_1$ exerts some force on a second charge $q_2$. If third charge $q_3$ is brought near, the force of $q_1$ exerted on $q_2$

1. Decreases
2. Increases
3. Remains unchanged
4. Increases if $q_3$ is of the same sign as $q_1$ and decreases if $q_3$ is of opposite sign

Q. Electric potential in a region is varying according to the relation $V=\frac{3x^2}{2}-\frac{y^2}{4}$ , where $x$ and $y$ are in $\text{meter}$ and $V$ is in $\text{volt}$. Electric field intensity in $\text{N/C}$ at a point $(1\text{m},2\text{m})$ is

1. $3\hat{i}-\hat{j}$
2. $-3\hat{i}+\hat{j}$
3. $6\hat{i}-2\hat{j}$
4. $-6\hat{i}+2\hat{j}$

Q.

A spherical volume contains a uniformly distributed charge of volume density $2.0\times {10}^{-4}C{m}^{-3}$. Find the strength of electric field at a point inside the volume at a distance $4.0cm$ from the centre.

1. $3\times {10}^4\frac{N}{C}$

2. $3\times {10}^5\frac{N}{C}$

3. $3\times {10}^6\frac{N}{C}$

4. $3\times {10}^7\frac{N}{C}$

Q. The centres of two identical small conducting spheres are 1m apart. They carry charges of opposite kind and attract each other with a force F. When they are connected by a conducting thin wire they repel each other with a force F/3. What is the ratio of magnitude of charges carried by the spheres initially?

Q. $\text{N}$ drops of mercury of equal radii and possessing equal charges combine to form a big spherical drop. If each individual drop has capacitance $C$ , then the capacitance of the bigger drop compared to each individual drop is

1. $\text{N}$ times
2. ${\text{N}}^{\frac{2}{3}}$ times
3. ${\text{N}}^{\frac{1}{3}}$ times
4. ${\text{N}}^{\frac{5}{3}}$ times

Q. An electric line of force in the xy plane is given by equation $x^2+y^2=1$. A particle with unit positive charge, initially at rest at the point x = 1, y = 0 in the xy plane

1. Will move along the circular line of force
2. Information is insufficient to draw any conclusion
3. Not move at all
4. Will move along straight line

Q.

A charged oil drop is suspended in a uniform field of $3\times {10}^{4}V/m$ so that it neither falls nor rises. The charge on the drop will be,

(Take $massofcharge=9.9\times {10}^{-15}kg$ and $g=10m/s^2$)

1. $3.3\times {10}^{-18}C$

2. $3.2\times {10}^{-18}C$

3. $1.6\times {10}^{-18}C$

4. $4.8\times {10}^{-18}C$

Q. A mass $m=20\text{g}$ has a charge $q=3.0\text{mC}$. It moves with a velocity of $20\text{m/s}$ and enters a region of electric field of $80\text{N/C}$ in the same direction as the velocity of the mass. The velocity of the mass after $3\text{sec}$ in this region is–

1. $80\text{m/s}$
2. $56\text{m/s}$
3. $44\text{m/s}$
4. $40\text{m/s}$