CBSE Class 12 Physics Electric Charges And Fields Worksheet Set A

Question. An electric shock is experienced on opening the door of a car due to
a) heating of car engine
b) discharge of electric charge
c) motion of car
d) None of the above

Answer : B

Question. If two bodies are rubbed and one of them acquires q₁charge and another acquires q2 charge, then ratio of q₁ : q₂ is
a) 1 : 2
b) 2 : 1
c) - 1 : 1
d) 1 : 4

Answer : C

Question. The ratio of electric fields on the axis and at equator of an electric dipole will be
a) 1 : 1
b) 2 : 1
c) 4 : 1
d) None of these

Answer : B

Question. In charging by induction,
a) body to be charged must be an insulator
b) body to be charged must be a semiconductor
c) body to be charged must be a conductor
d) any type of body can be charged by induction

Answer : C

Question. The Coulomb’s law is based on the assumption that
charges are treated as
a) positive charges
b) negative charges
c) neutral charges
d) point charges

Answer : D

Question. If point charges Q₁  = 2×10^_-7 C and Q₂= 3 ×10^_-7 C are at 30 cm separation, then find electrostatic force between them.
a) 2 × 10^-3 N
b) 6 × 10^-3 N
c) 5 × 10^-3 N
d) 1 × 10^-3 N

Answer : B

Question. A soap bubble is given a negative charge, then its radius
a) decreases
b) increases
c) remains unchanged
d) nothing can be predicted as information is insufficient

Answer : B

Question. For two charges q₁ and q₂, if force between them for some separation in air is F, then force between them in a medium of permittivity e will be
a) ε^₀/ε F
b) ε/ε^₀ F
c) εε^₀ F
d) F/ε^₀ε

Answer : A

Question. When the charge of a body becomes half, the electric field becomes
a) half
b) twice
c) thrice
d) No change

Answer : A

Question. Two field lines can never cross each other because
a) field lines are closed curves
b) field lines repels each other
c) field lines crowded only near the charge
d) field has a unique direction at each point

Answer : D

Question. The electric field at a point is
a) always continuous
b) continuous, if there is no charge at that point
c) continuous, if there is a charge at that point
d) None of the above

Answer : B

Question. The surface charge density s of an area element ignores
a) the quantisation of charge
b) discontinuity in charge distribution at macroscopic level
c) discontinuity in charge distribution at microscopic level
d) Both (a) and (c)

Answer : D

Question. A hollow metal sphere of radius R is uniformly charged.
The electric field due to the sphere at a distance r from the centre
a) zero as r increases for r < R, decreases as r increases for r > R
b) zero as r increases for r < R, increases as r increases for r > R
c) decreases as r increases for r < R and for r > R
d) increases as r increases for r < R and for r > R

Answer : A

Question. A uniformly charged conducting sphere of 2. 4m diameter has a surface charge density of 80 mCm-2.
What is the charge on the sphere?
a) 0.7 × 10 ^-1 C
b) 1.4 × 10 ^-2 C
c) 1.4 × 10 ^-3 C
d) 1.7 × 10⁴ C

Answer : C

Question. Total electric flux coming out of a unit positive charge put in air is
a) ε_⁰ ε_⁰/ε
b) ε^₀-1
c) (4pε_⁰ )^-1 pe 
d) 4πε_⁰

Answer : B

Question. A charged particle is free to move in an electric field. It will travel
a) always along a line of force
b) along a line of force, if its initial velocity is zero
c) along a line of force, if it has some initial velocity in the direction of an acute angle with the line of force
d) None of the above

Answer : B

Question. If ∫_S E.dS = 0 over a surface, then
a) the electric field inside the surface and on it is zero
b) the electric field inside the surface is necessarily uniform
c) the number of flux lines entering the surface must be equal to the number of flux lines leaving it
d) None of the above

Answer : C

Question. If same charge q is placed inside a sphere and cube having radius 1m and side 2m, respectively. What will be the ratio
of flux passing through them?
a) 1 : 1
b) 1 : 8
c) 8 : 1
d) 1 : 2

Answer : A

Question. What is the force between two small charged spheres having charges of 2 × 10^-7 C and 3 × 10 ^-7 C placed 30 cm apart in air?
a) 5 × 10^-2N
b) 6 ×10^-3N
c) 7 × 10^-4N
d) 8 × 10^-4N

Answer : B

Question. Two point charges q_A = 3μC and q_B = -3μC are located 20 cm apart in vacuum. What is the electric field at the mid-point O of the line AB joining the two charges?
a) 0
b) 2.7× 10⁶ (N/C)
c) 5.4 × 10⁶ (N/C)
d) 10.2 × 10⁶ (N/C)

Answer : C

Question. A point charge of20.μ C is at the centre of a cubic Gaussian surface 9.0 cm on edge. What is the net electric flux through the surface?
a) 0
b) 2 × 10² Nm² /C
c) 2 × 10⁴ Nm² /C
d) 2 × 10⁵ Nm² /C

Answer : D

Question. 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 × 10³ N/C and points radially inwards, what is the net charge on the sphere?
a) 0
b) 5 × 10^-5 C
c) 6 × 10^-9 C
d) 8 × 10^-10 C

Answer : C

Question. An infinite line charge produces a field of 9 × 10⁴ NC^-1 at a distance of 2 cm. Calculate the linear charge density.
a) 10^-5Cm^-1
b) 10^-6 Cm^-1
c) 10^-7 Cm^-1
d) 10^-8 Cm^-1

Answer : C