Chapter 12. Electricity

Class10 Science Chapter 12 Electricity Multiple Choice Questions and Answers :

Question : The unit of specific resistance of a material in S.I. system is : [SEBA 2015]

(a)   

(b)   

(c)  

(d)

Answer : (b)    

Question : Two wires have lengths , resistances , resistivities – each in the ratio 1:2 . what is the ratio of their diameters ?

(a) 1:2 

(b) 1:4 

(c) 4:1 

(d)

Answer :  (d)

[ We have, 

For first wire : 

For second wire : 

Question :  How many electrons will contribute in one second in causing on one micro-ampere of current ?[SEBA2017]

(a) 

(b)    

(c)   

(d) 

Answer :  (c)   .

[ Here,  microampere , second , coulomb .

We have,

  

   

Question :  An electron bulb is rated 220V and 100W . when it is operated on 110 V, then the power consumed is :[SEBA 2018]

(a) 75 W  

(b) 25 W 

(c) 100 W 

(d) 50 W

Answer : (d) 50 W

 [Here,

We have,   

Again, 

 

]

Question :  The practical unit of electrical energy 1 kWh means : [SEBA 2019]

(a)  J 

(b)  J  

(c)  J  

(d)  J

Answer : (b)  J   

Question :  The SI unit of electric charge is [SEBA 2021]

(a) Coulomb  

(b) Volt  

(c) Watt  

(d) Joule

Answer : (a) Coulomb .

Question :  Which of the following is used to measure the potential difference of a circuit ? [SEBA 2023]

(a) Ammeter   

(b) Voltmeter  

(c) Galvanometer  

(d) Multimeter

Answer : (b) Voltmeter  .

Question :  A cell, a resistor, a key and ammeter are arranged as shown in the circuit diagrams of Figure12.1. The current recorded in the ammeter will be

(a) maximum in (i)

(b) maximum in (ii)

(c) maximum in (iii)

(d) the same in all the cases

Answer : (d) the same in all the cases .

Question :  In the following circuits (Figure 12.2), heat produced in the resistor or combination of resistors connected to a 12 V battery will be

(a) same in all the cases

(b) minimum in case (i)

(c) maximum in case (ii)

(d) maximum in case (iii)

Answer : (c) maximum in case (ii)

Question :  Electrical resistivity of a given metallic wire depends upon

(a) its length

(b) its thickness

(c) its shape

(d) nature of the material

Answer : (d) nature of the material.

[ Electrical resistivity (ρ) is an intrinsic property of the material and is independent of the wire's length, thickness, or shape. It is a measure of how strongly a given material opposes the flow of electric current. Different materials have different resistivities, and this property is fundamental to the material itself.]

Question :  A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross section of the filament in 16 seconds would be roughly

(a)

(b) 

(c)

(d)

Answer : (a)

[ Here , I = 1 A , t = 16 s

We have,

Again,

]

Question :  Identify the circuit (Figure 12.3) in which the electrical components have been properly connected.

(a) (i)         (b) (ii)         (c) (iii)        (d) (iv)

Answer : (b) (ii)

Question :  What is the maximum resistance which can be made using five resistors each of 1/5 Ω?

(a) 1/5 Ω

(b) 10 Ω

(c) 5 Ω

(d) 1 Ω

Answer :  (d) 1Ω

[Here ,

  ]

Question :  What is the minimum resistance which can be made using five resistors each of 1/5 Ω?

(a) 1/5 Ω

(b) 1/25 Ω

(c) 1/10 Ω

(d) 25 Ω :

Answer :  (b) 1/25 Ω

 [  Here,

We have,

  ]

Question :  The proper representation of series combination of cells (Figure 12.4) obtaining maximum potential is

 

(a) (i)      (b) (ii)      (c) (iii)     (d) (iv)

Answer : (a)  (i)

Question :  Which of the following represents voltage?

(a)

(b)  Work done × Charge

(c)

(d) Work done × Charge × Time

Answer : (a)

Question :  A cylindrical conductor of length l and uniform area of cross- section A has resistance R. Another conductor of length 2l and resistance R of the same material has area of cross section

(a) A/2

(b) 3A/2

(c) 2A

(d) 3A

Answer :  (c) 2A.

[ We have,

 

Again,  ]

Question :  A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances  and   respectively (Figure.12.5). Which of the following is true?

(a) 

(b) 

(c) 

(d) 

Answer :  (c)  .

[ In a V-I (Voltage-Current) graph for resistors, the resistance (R) is given by the slope of the graph. The steeper the slope, the smaller the resistance. From the given options, the correct order of resistances based on the slopes of the V-I graphs is  .]

Question :  If the current I through a resistor is increased by 100% (assume that temperature remains unchanged), the increase in power dissipated will be

(a) 100 %         

(b) 200 %      

(c) 300 %       

(d) 400 %

Answer :  (c) 300%.

[ We have, 

If the current  is increased by 100%, the new current  will be .

The increase in power () is 

So, the increase in power is 300% of the original power . ]

Question :  The resistivity does not change if

(a) the material is changed

(b) the temperature is changed

(c) the shape of the resistor is changed

(d) both material and temperature are changed

Answer :  (c) the shape of the resistor is changed.

[ Resistivity (ρ) is an intrinsic property of a material and is independent of the material's shape. It also remains constant as long as the temperature remains constant. Therefore, if the shape of the resistor is changed, the resistivity of the material used to make the resistor will still stay the same.]

Question :  In an electrical circuit three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?

(a) Brightness of all the bulbs will be the same

(b) Brightness of bulb A will be the maximum

(c) Brightness of bulb B will be more than that of A

(d) Brightness of bulb C will be less than that of B

Answer : (c) Brightness of bulb B will be more than that of A.

[ In a parallel circuit, each bulb gets the full voltage of the source. The brightness of an incandescent bulb is directly proportional to its power. Therefore, the bulb with higher power (wattage) will be brighter. In this case, bulb B has a higher wattage (60 W) compared to bulb A (40 W), so the brightness of bulb B will be more than that of A.]

Question :  In an electrical circuit two resistors of 2 Ω and 4 Ω respectively are connected in series to a 6 V battery. The heat dissipated by the 4 Ω resistor in 5 s will be

(a) 5 J

(b) 10 J

(c) 20 J

(d) 30 J

Answer :  (c) 20 J.

[Here,  volt

 

We have,

 J

Therefore, the heat dissipated by the 4 Ω resistor in 5 s is 20 J. ]

Question :  An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?

(a) 1 A

(b) 2 A

(c) 4 A

(d) 5 A

Answer :  (d) 5 A.

[ We have ,

  and considering safety margins, a 5 A fuse is suitable.]

Question :  Two resistors of resistance 2 Ω and 4 Ω when connected to a battery will have

(a) same current flowing through them when connected in parallel

(b) same current flowing through them when connected in series

(c) same potential difference across them when connected in series

(d) different potential difference across them when connected in parallel

Answer : (b) same current flowing through them when connected in series.

[ In a series circuit, the current remains constant and resistances add up. ]

Question :  Unit of electric power may also be expressed as

(a) volt ampere

(b) kilowatt hour

(c) watt second

(d) joule second

Answer : (a) volt ampere .