Electricity mcq with Solution
1. True test of charging is :
(A) Attraction                        Â
(B) Repulsion
(C) Both attraction & repulsion                     Â
(D) None of the above
SolutionAns.    (B)
Sol.     Repulsion is a true test for electrification as one charged body can attract another uncharged body due to induction also.
2. Which of the following charge on an object is not possible :
(A) 3.2 × 10-19C                                            Â
(B) 4.8 × 10-19C
(C) 5.4 × 10-19 C                                           Â
(D) 8.0 × 10-19C
SolutionAns.    (C)
Sol.     Charge is quantised so, charge on any body should always be an integral multiple of charge on an electron.
3. A body is given positive charge :
(A) Its mass will increase                               Â
(B) Its mass will decrease
(C) Its mass will remain same                        Â
(D) None of these
SolutionAns.    (B)
Sol.     Body acquires positive charge due to removal of electrons so its mass will decrease.
4. Charge on 6.25 × 1018 electrons is :
(A) 1 coulomb                                              Â
(B) 2 coulomb
(C) 10 coulomb                                            Â
(D) 0.5 coulomb
SolutionAns.    (A)
Sol.     Charge on one electron = 1.6 × 10–19 C
Charge on 6.25 × 1018 electrons = {6.25 × 1018}×{1.6 × 10–19} = 1C
5. Which of the following is the S.I. unit of charge :
(A) Coulomb                                                 Â
(B) Ampere
(C) Volt
(D) Newton
Ans.    (A)
Sol.     S.I. unit of charge is coulomb.
6. Joule/coulomb is the unit of :
(A) Electric potential                                      Â
(B) Electric current
(C) Force                                                      Â
(D) Work
SolutionAns.    (A)
Sol.     S.I. unit of electric potential is J/C.
7. Tiny bits of paper are attracted by a charged comb due to :
(A) Conduction                                              Â
(B) Induction
(C) Convection                                             Â
(D) Radiation
SolutionAns.    (B)
Sol.     Tiny bits of paper are attracted by a charged comb due to Induction.
8. Law which gives magnitude of force between two charges is :
(A) Ohm’s law                                               Â
(B) Faraday’s Law
(C) Coulomb’s law                                         Â
(D) None of these
SolutionAns.    (C)
Sol.     Coulomb’s law gives the magnitude of electric force between two charged particles.
9. When a glass rod is rubbed with silk cloth :
(A) Glass rod gets positively charged            Â
(B) Silk cloth gets negatively charged
(C) Glass rod looses electrons
(D) All are correct
SolutionAns.    (D)
Sol.     When a glass rod is rubbed with silk cloth, it acquires positive charge while silk cloth gets negatively charged.
10. Cause of positive charge on a body is :
(A) Excess of electrons                                 Â
(B) Lack of electrons
(C) Excess of protons                                   Â
(D) Lack of protons
SolutionAns.    (B)
Sol.     A body gets positively charged by loosing electrons.
11. All equipments in households have :
(A) Same potential difference                        Â
(B) Same current
(C) Same power                                            Â
(D) Both (A) & (C)
SolutionAns.    (A)
Sol.     Same potential difference.
12. A positive charge released from rest :
(A) moves towards the regions of lower potential
(B) moves towards the regions of higher potential
(C) moves towards the regions of equal potential                                                       Â
(D) Does not move
SolutionAns.    (A)
Sol.     Positive charge always moves towards the region at lower potential from higher potential.
13. A battery is used to :
(A) Maintain a potential difference                  Â
(B) Measure electric current
(C) Measure electric potential                         Â
(D) Safeguard against short circuit
SolutionAns.    (A)
Sol.     Battery is used to maintain potential difference.
14. Two electric bulbs have resistances in the ratio 1 : 2. If they are joined in series, the energy consumed in them are in the ratio ………… :
(A) 1 : 2Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
(B) 1 : 1
(C) 2 : 1Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
(D) 4 : 1
SolutionAns.    (C)
Sol.     We know P = I2R
In series combination current is same for two resistances
∴  P \propto R \Rightarrow \frac{{{P_1}}}{{{P_2}}} = \frac{{{R_1}}}{{{R_2}}} \Rightarrow \frac{{{R_1}}}{{{R_2}}} = \frac{1}{2} .
15. On a body, charge can be produced by :
(A) Friction                                                    Â
(B) Induction
(C) Conduction
(D) All of the above
SolutionAns.    (D)
Sol.     Charge can be prodcued by any of A, B, C. So answer is D.
16. If distance between two charges increases, the value of force between them :
(A) Increases                                                 Â
(B) Decreases
(C) Remains un changed                                Â
(D) May increase or decrease
SolutionAns.    (B)
Sol.     F \propto \frac{1}{{{r^2}}} so when r increases, F decreases.
17. The path of free electron in a metal is :
(A) Parabolic                                                 Â
(B) Circular
(C) Straight line                                             Â
(D) Zigzag
SolutionAns.    (D)
Sol.     Zigzag (random motion).
18. Electric potential at point ‘A’ is 10 V & at point B is – 10 V. Find the work done by external agent in carrying 1 × 10–6 C of charge from A to B without acceleration ?
(A) 20 × 10–6 J                                              Â
(B) – 20 × 10–6 J
(C) 10 × 10–6 J                                              Â
(D) – 10 × 10–6 J
SolutionAns.    (B)
Sol.     W = qΔV = 1 × 10–6 [– 10 – (+ 10) ] = – 20 × 10–6
19. When a body is negatively charged by friction, it means :
(A) The body has acquired excess of electrons                                                          Â
(B) The body has acquired excess of proton
(C) The body has lost some electrons            Â
(D) The body has lost some neutrons
SolutionAns.    (A)
Sol.     Negative charge results from excess of electrons.
20. When a fuse is rated 8A, it means :
(A) It will not work if current is lessthan 8A
(B) It has a resistance of 8w                           Â
(C) It will work only if current is 8A
(D) It will melt if current exceeds 8A
SolutionAns.    (D)
Sol.     It will melt if current exceeds 8A.
21. Which of the following graph represents an ohmic device :
(A) Â Â Â Â Â
(B)
(C) Â Â
(D) Â
SolutionAns.    (A)
Sol.     For ohmic device I α V so graph is straight line and slope indicates electrical resistance.
22. Resistance depends upon:
(A) Nature of material of conductor                Â
(B) Length of conductor
(C) Area of cross section of conductor          Â
(D) All of the above
SolutionAns.    (D)
Sol.     R = \rho .\frac{l}{A}so answer is D.
23. How many electrons constitute current of one milliampere:
(A) 6.25 × 106                                                Â
(B) 6.25 × 1012                                              Â
(C) 6.25 × 109                                                Â
(D) 6.25 × 1015
SolutionAns.    (D)
Sol.     N = \frac{{1 \times {{10}^{ - 3}}}}{{1.6 \times {{10}^{ - 19}}}} = 6.25 \times {10^{15}}
24. An aluminium wire of definite length is stretched so that it’s diameter becomes half of initial diameter. Then what is it’s new resistance :
(A) Double                                                    Â
(B) Four times
(C) Eight times                                              Â
(D) Sixteen times
SolutionAns.    (D)
Sol.     Volume (A × l) remains constant on stretching
d2Â Â =\frac{{{d_1}}}{2} ;Â Â Â Â A2 =\frac{{{A_1}}}{4} ;Â Â {l_2} = 4 l1Â Â R2 = 16R1
25. Variation of current (I) and voltage (V) in a conductor has been shown in Fig. The resistance of the conductor is :
(A) 1Ω Â
(B) 2Ω
(C) 3Ω Â
(D) 4Ω
SolutionAns.    (C)
Sol.     R = \frac{{\Delta V}}{{\Delta I}} = \frac{{12}}{4} = 3\Omega
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