Electric Charges and Fields

Electric Charges and Fields Class 12 Physics MCQs

1. The surface considered for Gauss’s law is called
(a) Closed surface
(b) Spherical surface
(c) Gaussian surface
(d) Plane surface

2. The total flux through the faces of the cube with side of length a if a charge q is placed at corner A of the cube is

3. Which of the following statements is not true about Gauss’s law?
(a) Gauss’s law is true for any closed surface.
(b) The term q on the right side side of Gauss’s law includes the sum of all charges enclosed by the surface.
(c) Gauss’s law is not much useful in calculating electrostatic field when the system has some symmetry.
(d) Gauss’s law is based on the inverse square dependence on distance contained in the coulomb’s law

4. A charge Q is placed at the centre of the line joining two point charges +q and +q as shown in the figure. The ratio of charges Q and q is

(a) 4
(b) 1/4
(c) -4
(d) -1/4

5. The force per unit charge is known as
(a) electric flux
(b) electric field
(c) electric potential
(d) electric current

6. Electric field lines provide information about
(a) field strength
(b) direction
(c) nature of charge
(d) all of these

7. Which of the following figures represent the electric field lines due to a single negative charge?

8. The SI unit of electric flux is
(a) N C^-1 m^-2
(b) N C m^-2
(c) N C^-2 m²
(d) N C^-1 m²

9. The unit of electric dipole moment is
(a) newton
(b) coulomb
(c) farad
(d) debye

10. Consider a region inside which, there are various types of charges but the total charge is zero. At points outside the region
(a) the electric field is necessarily zero.
(b) the electric field is due to the dipole moment of the charge distribution only.
(c) the dominant electric field is inversely pro-portional to r3, for large r (distance from ori-gin).
(d) the work done to move a charged particle along a closed path, away from the region will not be zero.

11. SI unit of permittivity of free space is
(a) Farad
(b) Weber
(c) C²N^-1 m^-2
(d) C²N^-1 m^-2

12. The attraction is the real proof of an object being charged.
(a) True
(b) False
(c) a and b both
(d) None of these

13. If an object is positively charged, theoretically the mass of the object ______
(a) Increases slightly by a factor of 9.11*10^-31 kg
(b) Decreases slightly by a factor of 9.11*10^-31 kg
(c) Remains the same
(d) May increase or decrease

Question 14.
Which one of the following is the unit of electric field?
(a) Coulomb
(b) Newton
(c) Volt
(d) N/C

Question 15.
Three charges + 3q + q and Q are placed on a st. line with equal separation. In order to maket the net force on q to be zero, the value of Q will be :
(a) +3q
(b) +2q
(c) -3q
(d) -4q

Question 16.
If an electric dipole is kept in a uniform electric field then resultant electric force on it is :
(a) always zero
(b) never zero
(c) depend upon capacity of dipole
(d) None

Question 17.
The number of electron-taken out from a body to produce 1 coulomb of charge will be :
(a) 6.25 × 10¹⁸
(b) 625 × 10¹⁸
(c) 6.023 × 10²³
(d) None

Question 18.
The work done in rotating an electric dipole in an electric field:
(a) W = ME (1 – cos θ)
(b) W = ME tan θ
(c)W = ME sec θ
(d) None

Question 19.
If sphere of bad conductor is given charge then it is distributed on:
(a) surface
(b) inside the surface
(c) only inside the surface
(d) None

Question 20.
Electric field in a cavity of metal:
(a) depends upon the surroundings
(b) depends upon the size of cavity
(c) is always zero
(d) is not necessarily zero

Question 21.
The dielectric constant of a metal is:
(a) 0
(b) 1
(c) ∞
(d) -1

Question 22.
1 coulomb is equal to:
(a) 3 × 10⁹ e.s.u.
(b) \(\frac{1}{3}\) × 10⁹ e.s.u.
(c) 3 × 10¹⁰ e.s.u.
(d) \(\frac{1}{3}\) × 10¹⁰ e.s.u.

Question 23.
Each of the two point charges are doubled and their distance is halved. Force of interaction becomes p times, w here p is :
(a) 1
(b) 4
(c) \(\frac{1}{16}\)
(d) 16

Question 24.
Coulomb’s law in vector form can be written as
\(\vec{F} \) = (\(\frac{1}{4πε_n}\)) (\(\frac{q_1q_2}{r^2}\))\(\vec{r} \)
where ε₀ is the permitivity of free space. The SI units of ε₀ will be:
(a) N^-1m^-2C^-2
(b) Nm^-2C²
(c) N^-1m^-2C⁹.
(d) Nm^-2C²

Question 25.
The dimensional representation of cu will be :
(a) [MLT⁴ A²]
(b) [M^-1L^-3T⁴A²]
(c)[ML^-2T ]
(d) None of these

Question 26.
When placed in a uniform field, a dipole experiences:
(a) a net force
(b) a torque
(c) both a net force and torque
(d) neither a net force nor a torque

Question 27.
A parrot comes and sits on a bare high power line. It will:
(a) experience a mild shock ‘
(b) experience a strong shock.
(c) get killed instantaneously
(d) not be affected practically

Question 28.
The SI units of electric dipole moment are:
(a) C
(b) Cm^-1
(c) Cm
(d) Nm^-1

Question 29.
If two conducting sphere are connected after charging separately then:
(a) Electrostatic energy sphere energy will remain conserved
(b) Electrostatic energy charges remains conserved
(c) Electrostatic energy energy and charge remains conserved
(d) None

Question 30.
A soap bubble is given a negative charge, then its radius:
(a) increases
(b) decreases
(c) remains unchanged
(d) may increase or decrease

Question 31.
In non-uniform electric field, electric dipole experiences:
(a) torque only
(b) torque as well as net force
(c) force only
(d) None of these

Question 32.
An electron is sent in an electric field of magnitude 9.1 × 10⁶NC^-1. The acceleration produced in it is :
(a) 1.6 ms^-2
(b) 1.6 × 10¹⁸ms^-2
(c) 3.2 × 10¹⁸ms^-2
(d) 0.8 × 10¹⁸ ms^-2

Question 33.
A semicircular arc of radius r is charged uniformly and the charge per unit length is λ. The electric field at the centre is:
(a) \(\frac{λ}{2λε_0r^2}\)
(b) \(\frac{λ}{4πε_0r}\)
(c) \(\frac{λ^2}{2πε_0r}\)
(d) \(\frac{λ}{2πε_0r}\)

Question 34.
When a dipole of moment \(\vec{p} \) is placed in uniform electric field \(\vec{E} \), then the torque acting on the dipole is:
(a) \(\vec{τ} \) = \(\vec{p} \).\(\vec{E} \)
(b) \(\vec{τ} \) = \(\vec{P} \) + \(\vec{E} \)
(c) \(\vec{τ} \) = \(\vec{p} \) + \(\vec{E} \)
(d ) \(\vec{τ} \) = \(\vec{p} \) – \(\vec{E} \)

Question 35.
Two point charges +8q and -2q are located at ,v = O and ,v = L respectively. The location of a point on the .v-axis at which the net electric field due to these two point charges b is zero :
(a) 4L
(b) 8L
(c) L/4
(d) 2L

Question 36.
The graph drawn between V are r for a non-conducting charged solid sphere of radius R for r < R will be :
(a) straight line
(b) parabola
(c) hyperbola
(d) None of these

Question 37.
Corona discharge takes place:
(a) at the surface of a conductor
(b) near the sharp points of a conductor
(c) outside the conductor
(d) at the centre of the conductor

Question 38.
The belt of a Vande Graaf generator gets charge by :
(a) corona discharge
(b) induction
(c) electrification
(d) None of these

Question 39.
Quantisation of charge implies:
(a) Charge does not exist
(b) Charge exists on particles
(c) There is a minimum permissible magnitude of charge
(d) Charge can’t be created

Question 40.
The conservation of electric charge implies that:
(a) Charge can’t be created
(b) Charge can’t be destroyed
(c) The number of charged particle in the universe is constant
(d) Simultaneous creation of equal and opposite charges is permissible

Question 41.
The number of electrons contained in one coulomb of charge is:
(a) 6.25 × 10¹⁸
(b) 6.25 × 10¹⁷
(c) 6.25 × 10¹⁹
(d) 1.6 × 10¹⁹

Question 42.
The unit of intensity of electric field is :
(a) metre/volt
(b) Joule/newton
(c) Coulomb/newton
(d) Newton/coulomb

Question 43.
1 V equals to:
(a) 1 J
(b) 1 JC^-1
(c) 1 CJ^-1
(d) 1 JC

Question 44.
1 V m^-1 equals to:
(a) 1 N
(b) 1 Mm^-1
(c) 1 NC^-1
(d) 1 J^-1

Question 45.
The minimum amount of charge observed so far is:
(a) 1 C
(b) 4.8 × 1^-13 C
(c) 1.6 × 10^-19 C
(d) 1.6 × 10¹⁹ C

Question 46.
The ratio of electric force between two electrons to the gravitational force between them is of the order:
(a) 10⁴²
(b) 10³⁹
(c) 10³⁶
(d) 1