Electric Charges and Fields Class 12 MCQs Questions with Answers
Question 1.
Which one of the following is the unit of electric field?
(a) Coulomb
(b) Newton
(c) Volt
(d) N/C
Answer
Answer: (d) N/C
Question 2.
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
Answer
Answer: (a) +3q
Question 3.
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
Answer
Answer: (a) always zero
Question 4.
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
Answer
Answer: (a) 6.25 × 1018
Question 5.
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
Answer
Answer: (a) W = ME (1 – cos θ)
Question 6.
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
Answer
Answer: (d) None
Question 7.
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
Answer
Answer: (d) is not necessarily zero
Question 8.
The dielectric constant of a metal is:
(a) 0
(b) 1
(c) ∞
(d) -1
Answer
Answer: (c) ∞
Question 9.
1 coulomb is equal to:
(a) 3 × 109 e.s.u.
(b)
(c) 3 × 1010 e.s.u.
(d)
Answer
Answer: (a) 3 × 109 e.s.u.
Question 10.
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)
(d) 16
Answer
Answer: (d) 16
Question 11.
Coulomb’s law in vector form can be written as
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
Answer
Answer: (c) N-1m-2C9
Question 12.
The dimensional representation of cu will be :
(a) [MLT4 A2]
(b) [M-1L-3T4A2]
(c)[ML-2T ]
(d) None of these
Answer
Answer: (b) [M-1L-3T4A2]
Question 13.
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
Answer
Answer: (b) a torque
Question 14.
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
Answer
Answer: (d) not be affected practically
Question 15.
The SI units of electric dipole moment are:
(a) C
(b) Cm-1
(c) Cm
(d) Nm-1
Answer
Answer: (c) Cm
Question 16.
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
Answer
Answer: (b) Electrostatic energy charges remains conserved
Question 17.
A soap bubble is given a negative charge, then its radius:
(a) increases
(b) decreases
(c) remains unchanged
(d) may increase or decrease
Answer
Answer: (a) increases
Question 18.
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
Answer
Answer: (b) torque as well as net force
Question 19.
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
Answer
Answer: (b) 1.6 × 1018ms-2
Question 20.
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)
(b)
(c)
(d)
Answer
Answer: (b)
Question 21.
When a dipole of moment
(a)
(b)
(c)
(d )
Answer
Answer: (c)
Question 22.
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
Answer
Answer: (d) 2L
Question 23.
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
Answer
Answer: (d) None of these
Question 24.
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
Answer
Answer: (b) near the sharp points of a conductor
Question 25.
The belt of a Vande Graaf generator gets charge by :
(a) corona discharge
(b) induction
(c) electrification
(d) None of these
Answer
Answer: (a) corona discharge
Question 26.
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
Answer
Answer: (c) There is a minimum permissible magnitude of charge
Question 27.
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
Answer
Answer: (d) Simultaneous creation of equal and opposite charges is permissible
Question 28.
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
Answer
Answer: (a) 6.25 × 1018
Question 29.
The unit of intensity of electric field is :
(a) metre/volt
(b) Joule/newton
(c) Coulomb/newton
(d) Newton/coulomb
Answer
Answer: (a) metre/volt
Question 30.
1 V equals to:
(a) 1 J
(b) 1 JC-1
(c) 1 CJ-1
(d) 1 JC
Answer
Answer: (b) 1 JC-1
Question 31.
1 V m-1 equals to:
(a) 1 N
(b) 1 Mm-1
(c) 1 NC-1
(d) 1 J-1
Answer
Answer: (c) 1 NC-1
Question 32.
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
Answer
Answer: (c) 1.6 × 10-19 C
Question 33.
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
Answer
Answer: (a) 1042
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