Chapter 13: Electrostatics

     Chp 13: Electrostatics

Answer the following questions.

1. How can you show by a simple experiment that there are two types of charges?

Ans.  Experiment at pg 69

2. Describe the method of charging through electrostatic induction?

Ans. There are a variety of methods to charge an object. One method is known as induction. In the induction process, a charged object is brought near but not touched to a neutral conducting object. The presence of a charged object near a neutral conductor will force (or induce) electrons within the conductor to move.

Take two insulator conductors or neutral bodies fixed on a stand and bring a postively charged rod near to it eventually it will attract the unlike charges causing the negative charge to come near to rod while the like charge i.e the positive charges will move at the opposite end of the bodies.

3. What is Gold leaf electroscope? discuss its working principle with the help of a diagram. 

Ans.  “The gold leaf electroscope is sensitive instrument for detecting charges”.

Working:  

 Electroscope consists of closely placed two metallic (aluminium) foils or strips. When both the strips are charged with similar charges, they repel each other and become wide on

4.  With the help of electroscope how can you find presence of charge on the body?

Ans.  pg 72 (In order to detect ........... amount of charge on the body)

5.How can you find the nature of charge on the body?

Ans.   pg 72  ( for the detections of charge....................  the body has negative charge)

6. Explain Coulomb’s law of electrostatics and write its mathematical form?

Ans. “The force of attraction or repulsion between two point charges is directly

proportional to the product of the magnitude of charges and inversely proportional to the

square of the distance between them”.

Mathematically :

Mathematical form: If there are two point charges q1 and q2, separated by a distance (r),

then the electrostatic force F between the charges.

F ∝ q1 q2

Force ∝ 1/ d2

F = k q1q2/ d2

7. What is meant by Electric field and Electric intensity?

Ans.    Electric field :

The electric field is a region around a charge in which it exerts electrostatic force on another charges.

       Electric field Intensity:

The strength of electric field at any point in space is known as electric field intensity.

8. What is difference between variable and fixed type capacitor?

Ans.   A fixed capacitor is constructed in such manner that it possesses a fixed value of

capacitance which cannot be adjusted. While in variable type of capacitors some

arrangement is made to change the area of the plates facing each other.

9. Enlist some Uses of capacitors?

Ans.  Uses of Capacitors:

• Capacitors are used for tuning transmitters, receivers and transistor radios.
• Capacitors are used in electronic circuits of computers.
• Capacitors are used to differentiate high and low frequency.

10. Derive the formula for the equivalent capacitance for a series combination ofa number of capacitors?

Ans: In this combination, the capacitors are connected side by side..    

V = V1 + V2 + V3

V = Q/C1 + Q/C2+ Q/C3

V = Q(1/C1 + 1/C2 + 1/C3)

V/Q = 1/C1 + 1/C2 + 1/C3

1/ Ceq =   1/C1 + 1/C2 + 1/C3

11. Define the hazards of electricity ?

Ans .    pg 85 both heading imp

12. How would you define Potential difference between two points? Define its unit.

Ans.  Potential difference between two points becomes equal to the energy supplied by

the charge. Thus, we define potential difference between two points as the energy supplied by a unit charge as it moves from one point to the other in the direction of the field.

Unit: Unit of potential difference is Volt.

17. What do you mean by the Capacitance of a capacitor? Define units of capacitance.

Ans. Capacitance of capacitor is defined as “the ability of the capacitor to store charge”.

It is given ratio of charge and the electric potential as:

          C = Q/V

Unit: SI unit of capacitance is farad.