Electric Charges and Fields - Online Test

Q1. In charging by Induction
Answer : Option B
Explaination / Solution:

If a charged object placed near an uncharge object than redistribution of charge takes place in uncharge object and if we will earthed one surface of uncharged object than one charge goes to earth and other charge spread on its surface and it becomes charged.

Q2. For charges  separated by a distance R the magnitude of the electrostatic force is given by 
Answer : Option D
Explaination / Solution:

According to Coulomb’s law the force between two point charges is

(a) The force is directly proportional to the product of magnitude of charges i.e.

(b) The force is inversly proportional to the square of distance between two charges i.e. 

Combining both


OR


Where k is a constant of proportionality known as force constant having different value in different systems


Q3. The unit of charge is
Answer : Option C
Explaination / Solution:

The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 6.242×1018 e (e is the charge of a proton).

Hence, the charge of an electron is approximately −1.602×10−19 C. The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere within one second. The symbol Q is often used to denote a quantity of electricity or charge.


Q4. Electric field at a point is defined as
Answer : Option B
Explaination / Solution:

Electric field intensity of a charge at a point is given by the force exerted by that charge on test charge or unit charge at that point
That is The electric field intensity of charge q is


Q5. According to superposition of electric fields
Answer : Option B
Explaination / Solution:

When several electric fields are working on single charge then the total electric field intensity on that charge is given by the vector sum of all electric field intensities 
Q6. Electric field lines can be said to be
Answer : Option A
Explaination / Solution:

Electric Field Lines can be defined as a curve which shows direction of electric field, when we draw tangent at its point. The concept of electric field was proposed by Michael Faraday, in the 19th century. He always thought that electric field lines can be used to describe and interpret the invisible electric field. Instead of using complex vector diagram every time, This pictorial representation or form is called electric field lines. Electric field lines can be used to describe electric field around a system of charges in a better way.

Q7. At any point on S on an electric field line
Answer : Option B
Explaination / Solution:

When a tangent is drawn at any point on field line then that tangent gives the direction of electric field at that point


Q8. An electric dipole is
Answer : Option C
Explaination / Solution:

An electric dipole is a separation of positive and negative charges. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some (usually small) distance. A permanent electric dipole is called an electret

Q9. The direction of an electric dipole
Answer : Option C
Explaination / Solution:

Dipole Moment— It is a vector quantity and is directed from negative charge to positive charge along the axis. It is denoted as pand is defined as the product of the magnitude of either of the charge and the dipole length i.e.
Q10. Electric flux
Answer : Option A
Explaination / Solution:

Flux—It means flow Electric Flux—The number of electric field lines passing through any area normally known as electric flux. It is given by ϕ=E × area flux is a scalar quantity