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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 901. |
In a parallel-plate capacitor, the region between the plates is filled by a dielectric slab. The capacitor is charged from a cell and then disconnected from it. The slab is now taken out. (a) The potential difference across the capacitor is reduced. (b) The potential difference across the capacitor is increased. (c) The energy stored in the capacitor is reduced. (d) No work is done by an external agent in taking the slab out. |
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Answer» Correct Answer is: (b) |
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| 902. |
In a parallel-plate capacitor, the region between the plates is filled by a dielectric slab. The capacitor is connected to a cell and the slab is taken out. (a) Some charge is drawn from the cell.(b) Some charge is returned to the cell.(c) The potential difference across the capacitor is reduced. (d) No work is done by an external agent in taking the slab out. |
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Answer» Correct Answer is: (b) Some charge is returned to the cell. When the dielectric slab is taken out, the capacitance decreases. Hence charge decreases, and the difference in charge is returned to the cell. |
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| 903. |
The strength of a dielectric is defined as the maximum electric intensity which it can withstand. A parallel-plate capacitor of plate area A on one side is filled with a dielectric of strength E and permittivity ε. The maximum charge which can be given to the capacitor is (a) εEA (b) EA/ε (c) E/εA (d) εE/A |
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Answer» Correct Answer is (a) εEA Let K = dielectric constant, ε = ε0K. σ = Q/A E = σ/ε0K or Q = εEa |
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| 904. |
What is : (a) the highest (b) the lowest total resistances that can be obtained by combinations of four coils of resistances `4 Omega,8 Omega,12 Omega,24 Omega` ? |
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Answer» There are four of resistances `4 Omega, 8 Omega, 12 Omega "and " 24 Omega` respectively. (a) If these coils are connected in series, then the equivalent resistance will be the highest, given by sum `4 + 8 + 12 + 24 = Omega`respectively. (a) If these coils are connected in series. then equivalent resistance will be the highest, given by the sum `4 + 8 + 12 + 24 = 48 Omega` (b) If these coils are connected in parallel, then the equivalent resistance will be the lowest, given by `1/(1/4+1/8+1/12+1/24)=1/((6+3+2+1)/(24))=24/12=2 Omega` Therefore, ` 2 Omega` is the lowest total resistance. |
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| 905. |
What is : (a) the highest (b) the lowest total resistances that can be secured by combinations of four coils of resistances `4 Omega,8 Omega,12 Omega,24 Omega` ? |
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Answer» (a) The highest resistance is secured when all the four coils are connected in series. In that case, `R_s = 4 Omega + 8 Omega + 12 Omega + 24 Omega = 48 Omega` (b) The lowest resistance is secured when all the four coils are connected in parallel. In that case, `(1)/(R_p) = (1)/(4)+(1)/(8)+(1)/(12)+(1)/(24) = (6+3+2+1)/(24) = (12)/(24)`, where `R_p = (24)/(12) Omega = 2 Omega`. |
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| 906. |
A wire that has resistance R is cut into two equal pieces. The two parts are joined in parallel. What is the resistance of the combination ? |
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Answer» Resistance of each part is R/2. Resultant resistance R’ is given by 1/R’ = 2/R+2/R R’=R/4. |
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| 907. |
A dielectric isA. a bad conductor of electricityB. a good conductor of electricityC. also called a capacitorD. an electric device having two magnetic poles |
| Answer» Correct Answer - A | |
| 908. |
An electric device which convers chemical energy into electrical energy is `"________"`.A. a D.C. generatorB. an A.C. generatorC. an electric cellD. Both (1) and (2) |
| Answer» Correct Answer - c | |
| 909. |
If the charge on two point charged bodies and the medium surrounding them are kept unchanged and the distance between them is reduced by `50%` then the force between them `"_____"`.A. is doubledB. is quadrupledC. becomes halfD. decreases to `1/4` th of their original force |
| Answer» Correct Answer - B | |
| 910. |
What would be the effect on the resistance of a metal wire of : (a) increasing its length ? (b) increasing its diameter ? (c) increasing its temperature ? |
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Answer» (a) Resistance will increase. (b) Resistance will decrease. (c) Resistance will increase. |
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| 911. |
Mention the differences between the combination of resistances in series and parallel. |
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| 912. |
On increasing the number of resistances connected in series, the total resistance of the series combination `"_______"`A. increasesB. decreasesC. remains the sameD. decreases with time |
| Answer» Correct Answer - A | |
| 913. |
State the law of combination of resistances in parallel. |
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Answer» According to the law of combination of resistance in parallel, the reciprocal of the combined resistance of a number of resistances connected in parallel is equal to the sum of the reciprocals of all the individual resistances. |
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| 914. |
State the law of combination of resistances in parallel. |
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Answer» Solution : According to the law of combination of resistance in parallel, the reciprocal of the combined resistance of a number of resistances connected in parallel is equal to the sum of the reciprocals of all the individual resistances. |
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| 915. |
If five resistances, each of value 0.2 ohm, are connected in series, what will be the resultant resistance ? |
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Answer» Solution : As per the law of combination of resistances in series, R=R1+ R2+ R3+ R4+ R5 R=0.2+0.2+0.2+0.2+0.2=1ohm. |
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| 916. |
How should the two resistances of 2 ohms each be connencted so as to produce an equivalent resistance of 1 ohm ? |
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Answer» Solution : Since the resultant resistance is less than the individual resistances, so the resistances should be connected in parallel. |
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| 917. |
Find out the folowing in the electric circuit given in (Fig. (a) Effective resistance of two `8 Omega` resistors in the combination (b) Current flowing through `4 Omega` resistor ( c) Potential difference across `4 Omega` resistance (d) Power dissipated in `4 Omega` resistor (e) Difference in ammeter readings, if any. . |
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Answer» (a) Since two `8 Omega` resistors are in parallel, their effective resistance `(R_p)` is given by `(1)/(R_p)=(1)/(8)+(1)/(8)=(1)/(4)` or `R_p = 4 Omega` (b) Total resistance in the circuit, `R = 4 Omega + R_p = 4 Omega + 4 Omega = 8 Omega` Current through the electric circuit, `I = (V)/( R) = (8 V)/(8 Omega) = 1 A` Since `4 Omega` resistor and `R_p` are in series, current through `4 Omega` resistors `= 1 A` (c) pd across `4 Omega` resistors, `V = IR = 1 xx 4 = 4 V` (d) Power dissipated in `4 Omega` resistors, `P = I^2 R = (1 A)^2 (4 Omega) = 4 W` (e) There is no difference in the readings of ammeters `A_1` and `A_2` as same current flows through all elements in a series curcuit. |
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| 918. |
What is the source of electric current in a T.V. remote? |
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Answer» Electric cell. |
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| 919. |
In which position is key placed in a circuit? |
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Answer» Key can be placed anywhere in the circuit. |
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| 920. |
Assertion and Reason.Assertion (A) : A current carrying wire should be charged. Reason (R) : The current in a wire is due to flow of free electrons in a definite direction.Mark the correct choice as (a) Both A and R are true but R is the correct explanation of assertion.(b) Both A and R are true but R is not correct explanation of assertion.(c) A is true but R is false.(d) A is false but R is true. |
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Answer» (d) A is false but R is true |
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| 921. |
What are the effects of electricity? |
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Answer» 1. Heating effect 2. Chemical effect 3. Magnetic effect |
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| 922. |
Fill in the blanks1. The direction of conventional current is _______ to electron flow. 2. One unit of coulomb is charge of approximately _______ protons or electrons. 3. _______ is used to measure the electric current. 4. In conducting materials electrons are ________ 5. S.I. unit of Electrical conductivity of a conductor is _______ |
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Answer» 1. Opposite 2. 6.242×10 3. Ammeter 4. Loosely 5. siemens/meter |
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| 923. |
Which one of the following phenomenon occurs when two naked wires of electricity supply line touch other? (a) Lightning (b) Short circuiting (c) Overloading(d) none |
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Answer» (b) Short circuiting |
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| 924. |
_______ was developed is 1887 by Yei Sakizo of Japan(a) Alkaline cell (b) Button cell(c) Lead accumulator (d) Dry cell |
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Answer» Correct asnwer is (d) dry cell |
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| 925. |
Which of the following is an electrical conductor? (a) cork (b) wood (c) plastic (d) silver |
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Answer» Correct answer is (d) silver |
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| 926. |
In an electric circuit, the current starts from (a) the positive terminal of the battery (b) the negative terminal of the battery (c) either of the terminals of the battery(d) none |
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Answer» (a) the positive terminal of the battery |
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| 927. |
A battery is a group of _______ (a) only two cells (b) only single cell(c) two or more cells (d) all of these |
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Answer» (c) two or more cells |
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| 928. |
What is a battery? |
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Answer» Batteries are a collection of one or more cells whose chemical reactions create a flow of electrons in a circuit. |
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| 929. |
Name few insulators. |
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Answer» Rubber, wood, plastic, glass. |
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| 930. |
(a) How is heat produced in a conductor by an electric current ? (b) What are the factors on which heat produced due to a current flowing through a conductor depend ? |
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Answer» (a) Heat produced in a conductor by an electric current is due to collisions of electrons with the ions in the conductor. (b) (i) Strength of current (ii) resistance of the conductor (iii) time for which current flows. |
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| 931. |
Write true or false for the statement:When, glass rod is rubbed with dry silk cloth, the electrons move from glass to silk. |
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Answer» True When the glass rod is rubbed with a dry silk cloth, the electrons move from glass to silk. |
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| 932. |
Write true or false for the statement:The cap of gold leaf electroscope is made of copper. |
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Answer» False The cap of gold leaf electroscope is made of copper. |
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| 933. |
A large number of free electrons are present in metals. Why is there no current in the absence of electric field across it ? |
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Answer» In the absence of an electric field, the motion of the electrons in a metal is random. There is no net flow of charge across any section of the conductor. So no current flows in the metal. |
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| 934. |
Can you charge an insulator by the method of conduction ? |
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Answer» No, we cannot charge an insulator by method of conduction. |
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| 935. |
Fill in the blanks(a) Like charges............. while unlike charges attract.(b) Mercury is a.............. of electricity while pure water is................. of electricity.(c) An ebonite rod when rubbed with fur acquires the.................charge.(d) When an uncharged conductor is brought in contact with the disc of a gold leaf electroscope, its leaves..................(e) Charge is shared in charging a conductor by the method of....................... |
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Answer» (a) Like charges repel while unlike charges attract. (b) Mercury is a conductor of electricity while pure water is insulator of electricity. (c) An ebonite rod when rubbed with fur acquires the negative charge. (d) When an uncharged conductor is brought in contact with the disc of a gold leaf electroscope, its leaves will remain unchanged. (e) Charge is shared in charging a conductor by the method of conduction. |
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| 936. |
Write true or false for the statement:If a glass rod rubbed with silk is brought near the cap of a negatively charged electroscope, the divergence of leaves will decrease. |
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Answer» If a glass rod rubbed with silk is brought near the cap of a negatively charged electroscope, the divergence of leaves will decrease. True |
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| 937. |
Write true or false for the statement:If a negatively charged rod is brought near a negatively charged pith ball electroscope, the pith ball will be stuck with the rod. |
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Answer» False. Correct: If a negatively charged rod is brought near a positively charged pith ball electroscope, the pith ball will be stuck with the rod. |
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| 938. |
Write true or false for the statement:An ebonite rod can be charged by touching it with a charged copper rod. |
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Answer» False. Correct: An ebonite rod can be charged by not touching it with a charged copper rod, will be charged by induction method. |
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| 939. |
Write true or false for the statement:To find whether the charge on a body is positive or negative, an uncharged electroscope is used. |
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Answer» False. Correct : To find whether the charge on a body is positive or negative, an charged electroscope is used. |
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| 940. |
Write true or false for the statement:To find whether a body is charged or not, an uncharged electroscope is used. |
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Answer» To find whether a body is charged or not, an uncharged electroscope is used. True |
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| 941. |
A and B are two identical conducting rods. A is given positive charge and B is connected to a cell as shown in the figure. Will there be any change in the electrostatic force between A and B if the switch is closed ? |
| Answer» There will be no electrostatic force between A and B. When switch is closed, electric current passes through B. The quantity of charge entering B is equal to the quanity of charge leaving B making it electrically neutral . And as charges in B are in motion, attraction between A and B of electrostatic induction is negligible. | |
| 942. |
An electroscope is used to find the _________ present on a body. |
| Answer» Correct Answer - Type of charge | |
| 943. |
Show that `1kWh = 3.6 MJ`A. 36B. 0.36C. 3.6D. 360 |
| Answer» Correct Answer - C | |
| 944. |
An electric motor convertsA. electrical energy into mechanical energy.B. mechanical energy into electrical energy.C. heat energy into electrical energy.D. None of the above |
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Answer» Correct Answer - A An electric motor is a device which converts electri-cal energy into mechanical energy. |
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| 945. |
The disadvantages of voltaic cells are _______ and ____________ . |
| Answer» Correct Answer - Polarization and local effect | |
| 946. |
In a dry cell which serves as a negative terminal? A) Zinc metal B) Carbon Rod C) Ammonium chloride D) Carbon powder |
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Answer» Correct option is A) Zinc metal |
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| 947. |
In a dry cell what serves as a positive terminal?A) Zinc metal B) Ammonium chloride C) Carbon powder D) Carbon Rod |
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Answer» Correct option is D) Carbon Rod |
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| 948. |
A neutral body gets charged when it brought into contact with a charged body. This method of charg-ing a body is called.A. charging by conductionB. charging by frictionC. charging by InductionD. None of the above |
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Answer» Correct Answer - A In charging by conduction method, a neutral body gets charged when it is brought into contact with a charged body. |
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| 949. |
Negative terminal of the dry cell is made of A) graphite B) copper C) zinc D) iron |
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Answer» Correct option is C) zinc |
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| 950. |
The brass of cap of the carbon and the zinc can of the dry cll act as `"_______"` and `"______"` poles, respectively.A. positive, negativeB. positive, positiveC. negative, positiveD. negative, negative |
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Answer» Correct Answer - A The brass cap of the carbon rod and the zinc can of the dry cell act as positive and negative poles, respectively. |
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