CBSE Class 10 Physics Electricity Assignment Set A

MULTIPLE-CHOICE QUESTIONS

Question. When electric current is passed, electrons move from:
(a) high potential to low potential.
(b) low potential to high potential.
(c) in the direction of the current.
(d) against the direction of the current.
Answer. B

Question. Electrical resistivity of any given metallic wire depends upon
(a) its thickness
(b) its shape
(c) nature of the material
(d) its length
Answer. C

Question. What is the commercial unit of electrical energy?
(a) Joules
(b) Kilojoules
(c) Kilowatt-hour
(d) Watt-hour
Answer. C

Question. The heating element of an electric iron is made up of:
(a) copper
(b) nichrome
(c) aluminium
(d) iron
Answer. B

Question. A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances R1 , R2 and R3 respectively. Which of the following is true?

(a) R1 = R2 = R3
(b) R1 > R2 > R3
(c) R3 > R2 > R1
(d) R2 > R3 > R1
Answer. C

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

Question. Coulomb is the SI unit of:
(a) Charge
(b) current
(c) potential difference
(d) resistance
Answer. A

Question. Work of 14 J is done to move 2 C charge between two points on a conducting wire. What is the potential difference between the two points?
(a) 28 V
(b) 14 V
(c) 7 V
(d) 3.5 V
Answer. c

Question. Calculate the current flow through the 10 Ω resistor in the following circuit.

(a) 1.2 A
(b) 0.6 A
(c) 0.2 A
(d) 2.0 A
Answer. B

Question. If R1 and R2 be the resistance of the filament of 40 W and 60 W, respectively operating 220 V, then
(a) R1 < R2
(b) R2 < R1
(c) R1 = R2
(d) R1 ≥ R2
Answer. B

Question. Two resistors connected in series give an equivalent resistance of 10 Ω. When connected in parallel, give 2.4 Ω. Then the individual resistance is
(a) each of 5 Ω
(b) 6 Ω and 4 Ω
(c) 7 Ω and 4 Ω
(d) 8 Ω and 2 Ω
Answer. B

Question. The resistance of a wire of length 300 m and cross-section area, 1.0 mm² made of material of resistivity 1.0 x 10⁻⁷ Ω is:
(a) 2 Ω
(b) 3 Ω
(c) 20 Ω
(d) 30 Ω
Answer. D

Question. Which of the given statements is true regarding ammeter and voltmeter?
(a) Ammeter is connected in series with the required device, Voltmeter in parallel
(b) Both ammeter and voltmeter are connected in series with required device
(c) The voltmeter is connected in series with the device, Ammeter in parallel
(d) They can be connected in any way
Answer. A

Question. The obstruction offered by material of conductor to the passage of electric current is known as :
(a) Resistance
(b) Conductance
(c) Inductance
(d) None of these
Answer. A

Question. The unit of potential difference is :
(a) Volt
(b) Ohm
(c) Ampere
(d) Faraday
Answer. A

Question. The instrument used for measuring electric current is :
(a) Ammeter
(b) Galvanometer
(c) Voltmeter
(d) Potentiometer
Answer. A

Question. While a cell is being charged, energy is converted into energy.
(a) mechanical, electrical
(b) electrical, chemical
(c) heat, electrical
(d) chemical, heat
Answer. B

Question. Copper is not preferred to make fuse wire because it .
(a) is a good conductor of electricity
(b) has a low melting point
(c) has a high melting point
(d) is not easily available
Answer. B

Question. Identify the correct circuit diagram:

(a) i
(b) ii
(c) iii
(d) iv
Answer. D

Question. The unit of resistivity is:
(a) V A
(b) V A
(c) V m /A
(d) VA/m
Answer. C

ASSERTION-REASON TYPE QUESTIONS
Following questions consist of two statements – Assertion (a) and Reason (R). Answer these questions selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of (a)
(b) Both A and R are true but R is not the correct explanation of (a)
(c) A is true but R is false.
(d) A is false but R is true.

Question. Assertion (a) : Longer wires have greater resistance and the smaller wires have lesser resistance.
Reason (R) : Resistance is inversely proportional to the length of the wire.-
Answer. C

Question. Assertion (a) : Tungsten metal is used for making filaments of incandescent lamps.
Reason (R) : The melting point of tungsten is very low.
Answer. C

Question. Assertion (a) : Alloys are commonly used in electrical heating devices, like electrical iron, toasters et(c)
Reason (R) : Alloys do not oxidise (burn) readily at high temperatures.
Answer. A

Question. Assertion (a) : Bending a wire does not affect electrical resistance.
Reason (R) : Resistance of a wire is proportional to resistivity of material.
Answer.  B

CASE STUDY BASED QUESTIONS

1.Electrical resistivities of some substances, at 20°C are given below in the table. Study the table and answer the given questions.

Question. Which is a better conductor of electric current ?
(a) Silver
(b) Copper
(c) Tungsten
(d) Mercury
Answer. A

Question. Which element will be used for electrical transmission lines ?
(a) Iron
(b) Copper
(c) Tungsten
(d) mercury 
Answer. B

Question. Nichrome is used in the heating elements of electric heating device because:
(a) It has high resistivity
(b) It does not oxidise readily at high temperature
(c) Both of the above
(d) None of the above 
Answer. C

Question. Series arrangement is not used for domestic circuits because:
(a) Current drawn is less
(b) Current drawn is more
(c) Neither of the above
(d) Both of the above
Answer. A
 

2. In the given circuit, three identical bulbs B1, B2 and B3 are connected in parallel with a battery of 4.5 V. Study the diagram and answer the questions given below:

Question. What will happen to the other two bulbs if the bulb B3 gets fused ?
(a) They will also stop glowing.
(b) Other bulbs will glow with same brightness.
(c) They will glow with low brightness.
(d) They glow with more brightness.
Answer. B

Question. If the wattage of each bulb is 1.5 W, how much readings will the ammeter A show when all the three bulbs glow simultaneously?
(a) 1.1 A
(b) 2.1 A
(c) 1.5 A
(d) None of the above
Answer. A

Question. Find the total resistance of the circuit.
(a) 1.0 Ω
(b) 4.1 Ω
(c) 1.5 Ω
(d) 2.0 Ω
Answer. B

Question. How many resistors of 88 Ω are connected in parallel to carry 10 A current on a 220 V line ?
(a) 2 resistors
(b) 1 resistors
(c) 3 resistors
(d) 4 resistors
Answer. D

(a): Which among iron and mercury is a better conductor?

Answer- Iron.

 

(b): Which material is the best conductor?

Answer- Silver.

 

Question : Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5 Ω resistor, an 8 Ω resistor, and a 12 Ω resistor, and a plug key, all connected in series.

Answer-

Question : Redraw the circuit of Question 12, putting in an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the 12 Ω resistor. What would be the readings in the ammeter and the voltmeter?

Answer-

R₁ = 5 Ω, R₂ = 8 Ω, R₃ = 12 Ω

As resistors are combines in series, So total resultant resistance is:

R = R₁ + R₂ + R₃ = 5 + 8 + 12 = 25 Ω

Now total current or reading of ammeter = I =  V/R =6/25 = 0.24 A

Now for 12 Ω Resistor, Reading of voltmeter = V = IR = 0.24 x 12 = 2.88 V.

Now equivalent resistance (R) for the circuit is:

More Question-

1. When does the current flow in an electric circuit?
2. What is the difference between resistance and resistor?
3. What are the factors on which the resistance of conductor depends? Give the corresponding relation.
4. Calculate the resistance of a 2m long nichrome wire of radius 0.321mm. Resistivity of nichrome is 15 x 10^-6 Ω m. If the potential difference of 10v is applied across this wire, what will be the current in the wire?
5. Derive an expression for the equivalent resistance of three resistances connected in series?
6. Derive an expression for the combination of three resistances connected in parallel.
7. Express Ohm’s law both by a mathematical formula and by a graph.
8. Derive an expression for the heat produced in a resistor R when a voltage drop across it is V. Hence state Joule’s law of heating.
9. Describe some practical applications of heating effect of the electric current.
10. An electrical heater is used on a 220v supply and takes a current of 5A
1. What is its power
2. What is the cost of using the heater for 50 hours if 1 KWh costs Rs. 1.50?
11. A house hold uses the following electric appliances :
i) Refrigerator of rating 400 W for 10 hours each day.
ii) Two electric fans of rating 80 W each for 12 hours each day.
iii) Six electric tubes of rating 18 W each for 6 hours each day.
Calculate the electricity bill of the house hold for the month of June if the cost per unit of electric energy is Rs. 3
12. Distinguish between kilowatt and kilowatt hour.
13. Define the term electric energy. Write an expression of the electric energy consumed in an electric circuit.
14. Define the term electric power. Write an expression for it.
15. Define kilowatt hour. How many joules are equal to 1 KWh.
16. Two identical resistors, each of resistance 10 Ohms are connected
i) in series ii) in parallel, in turns to a battery of 6 volts. Calculate the ratio of power consumed in the combination of resistors in two cases.