Electrostatics Short Questions and Answers

 

Electrostatics Short Questions and Answers. This post is about 2nd Year | FSc. Part-II Physics: (Electrostatics) | Short Questions and Answers. The following questions are very important for the final examinations of all Boards of Punjab as well as Pakistan:

Chapter No.1: Electrostatics

Short Questions and Answers

Q.1: The potential is constant throughout a given region of space. Is the electrical field zero or non-zero in this region? Explain.
Answer:
The electric field intensity is defined by the relation.
`E=-\frac{\triangle V}{\triangle r}` which states the negative of the potential gradient. If the potential constant throughout the given region of space then `\triangle V=0`.
So,          `E=\frac{0}{\triangle r}`
              `E=0`

Q.2: Suppose that you follow an electric field line due to a positive point charge. Do electric field and the potential increases?
Answer:
As we know that:
`E=\frac{1}{4\pi\epsilon_{\circ}} \frac{q}{r^2}`

Where, `\frac{q}{4\pi\epsilon_{\circ}}` = Constant

So, `E \propto \frac{1}{r^2}`

And `V=\frac{1}{4\pi\epsilon_{\circ}} \frac{q}{r}`

Where, `\frac{q}{4\pi\epsilon}` = Constant

So, `V \propto \frac{1}{r}`

Hence if we follow an electric line of force due to positive charge, the electric the intensity and electric potential decreases because both electric intensity and electric potential are inversely proportional to the distance `(E\propto\frac{1}{r^2}, V\propto\frac{1}{r})`.

Q.3: How can you identify that which plate of a capacitor is positively charged?
Answer:
The presence of a charge on a body is detected by a device called Gold Leaf Electroscope. If the disc of the electroscope is touched with any plate of the capacitor, the divergence of the leaves then the plate of the capacitor is positively charged.

OR

Another method for testing the charged plate of a capacitor, if a positive test charge is placed between the plates of a capacitor, the plate from which the charge moves away is a positively charged plate and the plate from which the charge moves towards is negatively charged plate.

Q.4: Describe the force or forces on a positive point charge when placed between parallel plates:
(a). With similar and equal charges?
(b). With opposite and equal charges?
Answer:

(a). In the case of similar and equal charges, when a positive point charge is placed between the parallel plates, the positive charge will remain in equilibrium due to equal and opposite forces as shown in the picture below.

(b). In the case of equal and opposite charges, the positive charge will move from positive charge will move from positive to the negative plate due to the forces acting along the same direction so the positive point charge moves towards the negative plate as shown in the below figure.

Q.5: Electric lines of force never cross. Why?
Answer:
No, the electric lines of force never cross each other. If the two electric lines of force may intersect at a point then there would be two values of intensity at the same time which is not correct. So electric lines of force never cross each other.

Q.6: If a point charge q of mass m is released in a non-uniform electric field with field lines in the same direction pointing, will it make a rectilinear motion?
Answer:

(a). If a point charge q of mass m is placed at any point in the non-uniform field created by a positive charge and negative charge then due to two equal and opposite charge, it will move along a curved path as shown in the below picture.

(b). If a point charge q of mass m placed at a point in a non-uniform field created by a negative charge -q or positive charge +q then the point charge will move in a straight line as shown in the below figure.

NOTE: 

The remaining short question and answers of Chapter No.1 (Electrostatics) will be published soon Insha Allah.

Attempt MCQs | Quiz of FSc Part-II, Physics Chapter No.1