Charging by Friction

Q. In a rectangular coordinate system a charge of 25 x 10^-9 C is placed at the origin of coordinates, and a charge of 25 x 10^-9 C is placed at a point x=6 cm, y=0. What is the electric field at (a) x=3m, y=0m (b) x=3m, y=4m?

Q. The current density at a point is $\overrightarrow{J}=(2\times {10}^4\hat{j}){\text{Am}}^{-2}$. Find the rate of charge flow through a cross-sectional area $\overrightarrow{S}=(2\hat{i}+3\hat{j}){\text{cm}}^2$.

1. $15$
2. $20$
3. $7$
4. $6$

Q. If a charged body is placed near a neutral conductor, then

1. It may repel or attract conductor, depending on its shape
2. It will not exert either attractive or repulsive force on conductor
3. It will repel the conductor
4. It will attract the conductor

Q. A neutral metal sphere is touched by a negatively charged metal rod. During the process, electrons are transferred from the ______ to the ______ and the sphere acquires a ______ charge.

1. charged rod, neutral sphere, positive
2. neutral sphere, charged rod, negative
3. neutral sphere, charged rod, positive
4. charged rod, neutral sphere, negative

Q. Five balls $\text{A, B, C, D}$ and $\text{E}$ are used in an experiment and following observations have been made :

$\left(1\right)$ Ball $\text{A}$ repels $\text{C}$ and attracts $\text{B}$.
$\left(2\right)$ Ball $\text{D}$ attracts $\text{B}$ and has no effect on $\text{E}$
$\left(3\right)$ A negatively charged rod attracts both $\text{A}$ and $\text{E}$.

Based on above information, select the correct charge configuration for balls (if any):
$\begin{array}{cccccc}& A& B& C& D& E\\ \left(\text{P}\right)& +& -& +& 0& +\\ \left(\text{Q}\right)& +& -& +& +& 0\\ \left(\text{R}\right)& +& -& +& 0& 0\\ \left(\text{S}\right)& -& -& -& 0& 0\end{array}$

1. $\text{P}$
2. $\text{R}$
3. $\text{S}$
4. $\text{Q}$

Q.

If an object made of substance A is rubbed with an object made of substance B, then A becomes positively charged and B becomes negatively charged. If, however, an object made of substance A is rubbed against an object made of substance C, then A become negatively charged. What will happen if an object made of substance B is rubbed against an object made of substance C?

1. B becomes positively charged and C becomes positively charged.

2. B becomes positively charged and C becomes negatively charged.

3. B becomes negatively charged and C becomes positively charged.

4. B becomes negatively charged and C becomes negatively charged.

Q. If a glass rod is rubbed with silk, it acquires a positive charge because :

1. Electrons are added to it
2. Protons are removed from it
3. Protons are added to it
4. Electrons are removed from it

Q. If a glass rod is rubbed with silk, it acquires a positive charge because :

1. Protons are added to it
2. Electrons are added to it
3. Electrons are removed from it
4. Protons are removed from it

Q.

If two bodies were rubbed against each other and one aquired a -5mC charge, what will be the charge on the other body?

1. +3mC

2. -5mC

3. +5mC

4. -3mC

Q. if we rub a glass rod with silk or wool , then the elctrons get transferred from glass rod to silk . why do electrons not get transferred from silk to glass rod ?