Which of the following statements about electric field lines (due to static charges) is incorrect?

1.	electric field lines never cross each other at any point.
2.	electric field lines do not form any closed loop.
3.	electric field lines can not be taken as continuous curves.
4.	electric field lines start from a positive charge and end on a negative charge.

A polythene piece rubbed with wool is found to have a negative charge of \(3 \times10^{-7}~\text{C}.\) Transfer of mass from wool to polythene is:
1. \(0.7\times10^{-18}~\text{kg}\)
2. \(1.7\times10^{-17}~\text{kg}\)
3. \(0.7\times10^{-17}~\text{kg}\)
4. \(1.7\times10^{-18}~\text{kg}\)

Two insulated charged copper spheres \(A\) and \(B\) have their centers separated by a distance of \(50 ~\text{cm}.\) What is the mutual force of electrostatic repulsion if the charge on each is  $\mathrm{}$\(6 . 5 × 10 ^{- 7}~\text C ?\) 
(the radii of \(A\) and \(B\) are negligible compared to the distance of separation.)
1. \(1.52 × 10^{−2}~\text N\)
2. \(3.7 × 10^{−2}~\text N\)
3. \(2.01 × 10^{−2}~\text N\)
4. \(2.23 × 10^{−1}~\text N\)

The figure below shows tracks of three charged particles in a uniform electrostatic field. Which particle has the highest charge to the mass ratio?

The electric field at the surface of a black box indicates that the net outward flux through the surface of the box is \(8.0\times10^{3}~\text {Nm}^{2}/\text C.\) What is the net charge inside the box?
1. \(1.01~\mu \text C\) 
2. \(0.01~\mu \text C\) 
3. \(0.03~\mu \text C\) 
4. \(0.07~\mu \text C\)

A point charge \(+ 10 μ\text C\) is at a distance \(5~\text{cm}\) directly above the centre of a square of side \(10~\text{cm},\) as shown in the figure. What is the magnitude of the electric flux through the square?

       
1. \(3.18\times10^5~\text{Nm}^2\text C^{-1}\)
2. \(2.10\times10^5~\text{Nm}^2\text C^{-1}\)
3. \(1.03\times10^5~\text{Nm}^2\text C^{-1}\)
4. \(1.88\times10^5~\text{Nm}^2\text C^{-1}\)

A point charge of 2.0 μC is at the center of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?

1. 2.26 × 10⁵  N  m² C^-1
2. 2.09 × 10⁵  N  m² C^-1
3. 4.33 × 10⁵  N  m² C^-1
4. 4.71 × 10⁵  N  m² C^-1   

A point charge causes an electric flux of \(-1.0\times 10^{3}~\text{Nm}^2/\text{C}\) to pass through a spherical Gaussian surface of \(10.0~\text{cm}\) radius centered on the charge. If the radius of the Gaussian surface were doubled, how much flux would pass through the surface?
1. \(- 2.0×10^{3}~\text{Nm}^2/\text{C}\)
2. \(- 1.0 ×10^{3}~\text{Nm}^2/\text{C}\)
3. \(2.0 ×10^{3}~\text{Nm}^2/\text{C}\)
4. Zero

A conducting sphere of radius \(10\) cm has an unknown charge. If the electric field, \(20\) cm from the centre of the sphere is \(1.5\times10^3\) N/C and points radially inward, what is the net charge on the sphere?