### NEET Physics - New - Electric Charges and Fields

#### Question - 1

A short electric dipole has a dipole moment of $16 \times 10^{9} \mathrm{~cm}$. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of $60^{\circ}$ with the dipole axis is:
$\left(\frac{1}{4 \pi \varepsilon_{0}}=9 \times 10^{9} \mathrm{Nm}^{2} / \mathrm{C}^{2}\right)$

• A zero
• B 50 V
• C 200 V
• D 400 V

#### Question - 2

A spherical conductor of radius 10 cm has a charge of $3.2 \times 10^{-7} \mathrm{C}$ distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere?
$\left(\frac{1}{4 \pi \epsilon_{0}}=9 \times 10^{9} \mathrm{Nm}^{2} / \mathrm{C}^{2}\right)$

• A $1.28 \times 10^{7} \mathrm{~N} / \mathrm{C}$
• B $1.28 \times 10^{4} \mathrm{~N} / \mathrm{C}$
• C $1.28 \times 10^{5} \mathrm{~N} / \mathrm{C}$
• D $1.28 \times 10^{6} \mathrm{~N} / \mathrm{C}$

#### Question - 3

Two point charges A and B, having charges +Q and -Q respectively, are placed at certain distance apart and force acting between them is F. If 25 % charge of A is transferred to B, then force between the charges becomes:

• A $\frac{9 \mathrm{~F}}{16}$
• B $\frac{16 \mathrm{~F}}{9}$
• C $\frac{4 \mathrm{~F}}{3}$
• D $\mathrm{F}$

#### Question - 4

Two parallel infinite line charges with linear charge densities $+\lambda \mathrm{C} / \mathrm{m}\text{ and }-\lambda \mathrm{C} / \mathrm{m}$ are placed at a distance of 2R in free space. What is the electric field mid-way between the two line charges?

• A $\frac{2 \lambda}{\pi \varepsilon_{0} \mathrm{R}} \mathrm{N} / \mathrm{C}$
• B $\frac{\lambda}{\pi \varepsilon_{0} \mathrm{R}} \mathrm{N} / \mathrm{C}$
• C $\frac{\lambda}{2 \pi \varepsilon_{0} \mathrm{R}} \mathrm{N} / \mathrm{C}$
• D Zero

#### Question - 5

The electric field in a certain region is acting radially outward and is given by E=Ar. A charge contained in a sphere of radius ' a ' centred at the origin of the field, will be given by:

• A $A \varepsilon_{0} a_{1}^{2}$
• B $4 \pi \varepsilon_{0} A a^{3}$
• C $\varepsilon_{0} A a^{3}$
• D $4 \pi \varepsilon_{0} \mathrm{Aa}^{2}$

#### Question - 6

An electric dipole of dipole moment p is aligned parallel to a uniform electric field E. The energy required to rotate the dipole by $90^{\circ}$ is _______________ .

• A $p E^{2}$
• B $p^{2} E$
• C pE
• D Infinity

#### Question - 7

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:

• A Q/2
• B -Q/4
• C Q/4
• D -Q/2

#### Question - 8

Two pith balls carrying equal charges are suspended from a common point by strings of equal length. The equilibrium separation between them is r. Now the strings are rigidly clamped at half the height. The equilibrium separation between the balls now become

• A $\left(\frac{r}{\sqrt[3]{2}}\right)$
• B $\left(\frac{2 r}{\sqrt{3}}\right)$
• C $\left(\frac{2 r}{3}\right)$
• D $\left(\frac{r}{\sqrt{2}}\right)^{2}$

#### Question - 9

Two metallic spheres of radii 1 m and 3 cm are given charges of $-1 \times 10^{-2} \mathrm{C}$  and $5 \times 10^{-2} \mathrm{C}$, respectively. If these are connected by a conducting wire, the final charge on the bigger sphere is:

• A $2 \times 10^{-2} \mathrm{C}$
• B $3 \times 10^{-2} \mathrm{C}$
• C $4 \times 10^{-2} \mathrm{C}$
• D $1 \times 10^{-2} \mathrm{C}$

#### Question - 10

What is the flux through a cube of side ' a ' if a point charge of q is at one of its corner:

• A $\frac{2 q}{\varepsilon_{0}}$
• B $\frac{q}{8 \varepsilon_{0}}$
• C $\frac{q}{\varepsilon_{0}}$
• D $\frac{q}{2 \varepsilon_{0}} 6 a^{2}$