ELECTRICITY - I :MCQs AND SHORT ANSWERS

MULTIPLE-CHOICE QUESTIONS

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SELECT THE CORRECT ALTERNATIVE:

1. Who had patented more than 1000 inventions during his life time ?
   
   
   
   1. Edison
   2. Volta
   3. Ampere
   4. Faraday
      
   
   
2. The unit of electric current is _______.
   
   
   
   1. coulomb
   2. volt
   3. ampere
   4. ohm
      
   
   


3. The unit of electric charge is _______.
   
   
   
   1. coulomb
   2. volt
   3. ampere
   4. ohm
      
   
   
4. The unit of electric current is _______.
   
   
   
   1. coulomb
   2. coulomb/sec
   3. coulomb-sec
   4. coulomb/volt
      
   
   
5. 1 ampere = _______.
   
   
   
   1. coulomb sec
   2. coulomb/sec
   3. volt/sec
   4. ohm/sec
      
   
   
6. Work done on an electric charge is stored in it as _______.
   
   
   
   1. potential energy
   2. kinetic energy
   3. thermal energy
   4. nuclear energy
      
   
   
7. The unit of electrical potential is _______.
   
   
   
   1. coulomb/joule
   2. joule/coulomb
   3. watt/coulomb
   4. joule/ampere
      
   
   
8. The unit of electrical potential is _______.
   
   
   
   1. ampere
   2. coulomb
   3. volt
   4. watt
      
   
   
9. _______ is not essential to obtain electric current.
   
   
   
   1. Free electrons
   2. Potential difference
   3. Electric circuit
   4. potential
      
   
   
10. _______ invented a simple electrochemical cell.
    
    
    
    1. Archimedes
    2. Edison
    3. Volta
    4. Coulomb
       
    
    
11. _______ energy is converted into electrical energy in Voltaic cell.
    
    
    
    1. Thermal
    2. Mechanical
    3. Kinetic
    4. Chemical
       
    
    
12. The unit of resistance is _______.
    
    
    
    1. volt/ampere
    2. coulomb/second
    3. volt/coulomb
    4. ampere/volt
       
    
    
13. The unit of resistance is _______.
    
    
    
    1. coulomb
    2. volt
    3. ohm
    4. ampere
       
    
    
14. When resistors are connected in series _______.
    
    
    
    1. voltage drop is uniform
    2. current is uniform
    3. both voltage and current are uniform
    4. neither of two is uniform
       
    
    
15. When resistors are connected in parallel _______.
    
    
    
    1. voltage drop is uniform
    2. current is uniform
    3. both voltage and current are uniform
    4. neither of two is uniform
       
    
    
16. Three resistors of 6 Ω, 12 Ω and 12 Ω are connected in parallel. Their equivalent resistance is _______.
    
    
    
    1. 6 Ω
    2. 12 Ω
    3. 3 Ω
    4. 1/3 Ω
       
    
    
17. Which of the following is not correct for electrical work ?
    
    
    
    1. W = VQ
    2. W = VIt
    3. W = I²Rt
    4. W = I²RQ
       
    
    
18. _______ is not a unit of energy.
    
    
    
    1. joule
    2. watt
    3. watt second
    4. kWh
       
    
    
19. 1 joule = _______.
    
    
    
    1. 1 watt-second
    2. 1 watt/second
    3. 1 coulomb/second
    4. 1 unit
       
    
    
20. Which of the following is not correct ?
    
    
    
    1. P = W/t
    2. P = I²R
    3. P = WI
    4. P = VI
       
    
    
21. Silicon is a/an _______.
    
    
    
    1. conductor
    2. insulator
    3. semiconductor
    4. superconductor
       
    
    
22. Who discovered electron ?
    
    
    
    1. Coulomb
    2. Volta
    3. Ampere
    4. Thomson
       
    
    
23. 1 A = _______ mA
    
    
    
    1. 100
    2. 10³
    3. 10^(-3)
    4. 10^(-6)
       
    
    
24. Ohm's law states that
    
    
    
    1. resistance increases as current increases
    2. resistance increases as voltage increases
    3. current increases as voltage increases
    4. current increases as resistamce increases
       
    
    
25. Equivalent resistance of resistances in parallel is _______.
    
    
    
    1. smaller than the smallest resistance
    2. larger than the largest resistance
    3. an average of all resistances
    4. algebraic sum of all resistances
       
    
    
26. 1 unit of domestic energy is _______.
    
    
    
    1. 1 joule
    2. 1 watt second
    3. 3.6 x 10⁶ j
    4. 3.6 x 10⁶ kwh
       
    
    
27. Three resistors of equal value are connected in parallel.The circuit current is 3 A.Then the current passing through each resistor is _______.
    
    
    
    1. 3 A
    2. 1 A
    3. 9 A
    4. 1/3 A
       
    
    
28. How much electric charge is present on 100 protons ?
    
    
    
    1. 6 x 10^-19 C
    2. 6 x 10^-17 C
    3. 1.6 x 10^-19 C
    4. 1.6 x 10^-17 C
       
    
    
29. Pure water is electrically...
    
    
    
    1. a good conductor
    2. a bad conductor
    3. a semiconductor
    4. a super conductor
       
    
    
30. The frequency of direct current in India is______ Hz.
    
    
    
    1. 0
    2. 50
    3. 60
    4. 220
       
    
    

ANSWERS


(1) A (2) C (3) A (4) B (5) B (6) A (7) B (8) C (9) D (10) C (11) D (12) A (13) C (14) B (15) A (16) C (17) D (18) B (19) A (20) C (21) C (22) D (23) B (24) C (25) A (26) C (27) B (28) D (29) B (30) A

SHORT QUESTIONS

ANSWER IN SHORT:

1. What type of charge does a glass rod acquire when it is rubbed with silk cloth ?
   
   ANS:A glass rod acquires positive charge when it is rubbed with silk cloth
   
   
2. what is an electric charge ?
   
   ANS:An electric charge is a fundamental property associated with protons and electrons.
   
   
3. What is the unit of electric charge ?
   
   ANS:The unit of electric charge is coulomb.
   
   
4. What is the magnitude of charge on proton ?
   
   ANS:The magnitude of charge on proton is 1.6 x 10^(-19).
   
   
5. What is the magnitude of charge on electron ?
   
   ANS:The magnitude of charge on electron is 1.6 x 10^(-19).
   
   
6. Mention some metals which contain maximum free electrons.
   
   ANS:Copper, aluminium and silver are the metals containing maximum free electrons.
   
   
7. What are conductors ?
   
   ANS:Conductors are materials which conduct electricity readily.
   
   
8. What are insulators ?
   
   ANS:Insulators are materials which do not conduct electricity.
   
   
9. Give some examples of insulators.
   
   ANS:Rubber, leather, plastic, glass, etc. are examples of insulators.
   
   
10. Define : Electric current.
    
    ANS:Electric current is the net amount of charge that passes through an area(cross-sectional area) of the conductor per unit time.
    
    
11. Who gave the concept of electron ?
    
    ANS:Sir J.J.Thomson gave the concept of electron.
    
    
12. How many electrons should flow in one second to contribute an electric current of 1 ampere ?
    
    ANS:6.25 x 10¹⁸ electrons should flow in one second to contribute an electric current of 1 ampere.
    
    
13. What should be done to get electric current ?
    
    ANS:Energy should be provided o the free electrons in a conductor to obtain electric current.
    
    
14. Define : Electric potential.
    
    ANS:At a point in an electric field, the electrical potential energy per unit charge is called the electrical potential at that point.
    
    
15. What is the direction of actual current ?
    
    ANS:The direction of actual current is from cathode to anode.
    
    
16. What is the direction of conventional current ?
    
    ANS:The direction of conventional current is from anode to cathode.
    
    
17. Define : Electrical potential difference.
    
    ANS:The work done to move a unit electric charge from one point of a conductor to another point of that conductor is called the electrical potential difference between these two points.
    
    
18. State Ohm's law.
    
    ANS:The current passing through a conductor is directly proportional to the potential difference (voltage drop) across the conductor.
    
    
19. Define : 1 ohm resistance.
    
    ANS:If a potential difference of 1 volt between two terminals of a conductor causes a current of 1 ampere in it, then the resistance of the conductor is 1 ohm.
    
    
20. On which factors does the heat produced in a conductor depend ?
    
    ANS:The heat produced in a conductor depends on the electric current and the resistance in it.
    
    
21. A fuse wire has a low melting point.True or false ?
    
    ANS:Yes, this is a true statement.
    
    
22. Define : Electric Power.
    
    ANS:Electrical energy consumed per unit time is called electric power.
    
    
23. What is the unit of power ?
    
    ANS:The unit of power is watt (or, joule/sec).
    
    
24. How many kj equal 1 kwh ?
    
    ANS:3.6 x 10³ kj equal 1 kwh.
    
    
25. How many joule equal 1 kwh ?
    
    ANS:3.6 x 10⁶ kj equal 1 kwh.
    
    
26. Pure water does not conduct electricity. True or false ?
    
    ANS:True, pure water does not conduct electricity.
    
    
27. The unit of electric charge is faraday. True or false ?
    
    ANS:False, the unit of electric charge is coulomb.
    
    
28. What are electrolytes ?
    
    ANS:The solutions that conduct electricity are known as electrolytes.
    
    
29. To which terminal is the object connected during electroplating ?
    
    ANS:The object is connected to the negative terminal(cathode) during electroplating.
    
    
30. What is electroplating ?
    
    ANS:The process of depositing a desired metal on another mettalic object by using electricity is called electroplating.
    
    
31. A fuse works on the principle of chemical effect of electric current. True ?
    
    ANS:No, a fuse works on the principle of thermal effect of electric current.
    
    
32. How do we get flow of electrons in a conductor ?
    
    ANS:We get flow of electrons in a conductor by connecting the conductor to a source of energy(a cell or battery) which drives free electrons in a definite direction.
    
    
33. Current flows in a wire.Can we call the wire charged ? Why ?
    
    ANS:No. Because the flow of current in a wire does not add or remove any charged particles in it.
    
    
34. What causes resistance in a conductor ?
    
    ANS:The collision of free electrons moving in a conductor with the atoms or molecules of the conductor causes resistance in a conductor.
    
    
35. Write the equations for equivalent resistance R of two resistors R₁ and R₂ connected in (i)series (ii)parallel.
    
    ANS:(i)Series: R = R₁ + R₂(ii)Parallel : (1/R) = (1/R₁) + (1/R₂)
    
    
36. Define the unit of electrical energy.
    
    ANS:The unit of electrical energy is joule and it is defined as : the electrical energy consumed when one coulomb of charge passes through a point in a conductor having 1 volt potential difference.
    
    
37. What type of wire should be used in a fuse ?
    
    ANS:A wire made from a low melting point metal/alloy having high resistance should be used in a fuse.
    
    
38. How much electric energy is spent if 200 units are consumed ?
    
    ANS:200 kwh or 200 x (3.6 x 10⁶) = 7.2 x 10⁸ j energy is spent if 200 units are consumed.
    
    
39. What is the principle of electroplating ?
    
    ANS:The principle of electroplating is that a metal can be deposited on the surface of another metal with the help of electrolysis.
    
    
40. What is electrolysis ?
    
    ANS:The process of separation of ions of a substance with the help of electric current is called electrolysis.
    
    
41. How much electric charge is present on 100 neutrons ?
    
    ANS:Zero.
    
    
42. Which effect of electric current is used in fuse ?
    
    ANS:The heating effect of electric current is used in fuse.
    
    
43. Write an expression for the amount of heat produced in a wire of resistance R and carrying current I for time t.
    
    ANS:Heat produced = I²Rt
    
    
44. What is meant by saying that the potential difference between two points is 1 volt ?
    
    ANS:The meaning of the statement is that 1 joule work needs to be done to move 1 coulomb of charge from one point to the another.