Chapter - 12
Electricity
( āĻŦিāĻĻ্āϝুā§ )
EXERCISES:-
( āĻŦ্āϝাāϝ়াāĻŽ:- )
1. A piece of wire of resistance R is cut into five equal parts. These parts are then connected in parallel. If the equivalent resistance of this combination is R, then the ratio R/R is -
( āĻĒ্ā§°āϤিā§°োāϧ āĻā§°-ā§° āϤাঁā§°ā§° āĻুāĻুā§°া āĻāĻা āĻĒাঁāĻāĻা āϏāĻŽাāύ āĻ ংāĻļāϤ āĻāĻা āĻšāϝ়। āĻāĻ āĻ ংāĻļāĻŦোā§° āϤাā§° āĻĒিāĻāϤ āϏāĻŽাāύ্āϤ⧰াāϞāĻাā§ąে āϏংāϝোāĻিāϤ āĻā§°া āĻšāϝ়। āϝāĻĻি āĻāĻ āĻŽিāĻļ্ā§°āĻŖāĻোā§° āϏāĻŽāϤুāϞ্āϝ āĻĒ্ā§°āϤিā§°োāϧ āĻšৈāĻে āĻā§°, āϤেāύেāĻš'āϞে āĻā§°/āĻā§° āĻ āύুāĻĒাāϤ āĻšৈāĻে - )
(a) 1/25 (b) 1/5 (c) 5 (d) 25
Answer:-
2. Which of the following terms does not represent electrical power in a circuit?
( āύিāĻŽ্āύāϞিāĻিāϤ āĻোāύāĻো āĻļāĻŦ্āĻĻāĻ āĻŦā§°্āϤāύীāĻāĻাāϤ āĻŦৈāĻĻ্āϝুāϤিāĻ āĻļāĻ্āϤি āĻĒ্ā§°āϤিāύিāϧিāϤ্āĻŦ āύāĻā§°ে? )
(a) FR (b) IR2 (c) VI (d) V/R
Answer:-
3. An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be
( āĻāĻা āĻŦৈāĻĻ্āϝুāϤিāĻ āĻŦাāϞ্āĻŦāĻ 220 āĻি āĻā§°ু 100 āĻĄāĻŦ্āϞিāĻ ā§°েāĻিং āĻĻিāϝ়া āĻšāϝ়। āϝেāϤিāϝ়া āĻāϝ়াāĻ 110 āĻি-āϤ āĻĒā§°িāĻাāϞāύা āĻā§°া āĻšāϝ়, āĻŦ্āϝāϝ় āĻā§°া āĻļāĻ্āϤি āĻš'āĻŦ )
(a) 100 W
(b) 75 W
(c) 50 W
(d) 25 W
Answer:-
4. Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. The ratio of heat produced in series and parallel combinations would be -
(āĻāĻে āĻĒāĻĻাā§°্āĻĨā§° āĻĻুāĻা āĻĒā§°িāĻŦাāĻšী āϤাঁā§° āĻā§°ু āϏāĻŽাāύ āĻĻৈā§°্āĻ্āϝ āĻā§°ু āϏāĻŽাāύ āĻŦ্āϝাāϏ⧰ āĻĒ্ā§°āĻĨāĻŽে āĻļৃংāĻāϞাāϤ āϏংāϝোāĻিāϤ āĻšāϝ় āĻā§°ু āϤাā§° āĻĒিāĻāϤ āĻāĻে āϏāĻŽ্āĻাā§ą্āϝ āĻĒাā§°্āĻĨāĻ্āϝ⧰ āĻāĻা āĻŦā§°্āϤāύীāϤ āϏāĻŽাāύ্āϤ⧰াāϞāĻাā§ąে āϏংāϝোāĻিāϤ āĻā§°া āĻšāϝ়। āĻļৃংāĻāϞা āĻā§°ু āϏāĻŽাāύ্āϤ⧰াāϞ āϏংāĻŽিāĻļ্ā§°āĻŖāϤ āĻā§āĻĒাāĻĻিāϤ āϤাāĻĒā§° āĻ āύুāĻĒাāϤ āĻš'āĻŦ - )
(a) 1:2
(b) 2:1
(c) 1:4
(d) 4:1
Answer:-
5. How is a voltmeter connected in the circuit to measure the potential difference between two points?
( āĻĻুāĻা āĻŦিāύ্āĻĻুā§° āĻŽাāĻā§° āϏāĻŽ্āĻাā§ą্āϝ āĻĒাā§°্āĻĨāĻ্āϝ āĻোāĻাā§° āĻŦাāĻŦে āĻŦā§°্āϤāύীāϤ āĻāĻা āĻāϞ্āĻāĻŽিāĻাā§° āĻেāύেāĻĻā§°ে āϏংāϝোāĻিāϤ āĻšāϝ়? )
Answer:-
6. A copper wire has diameter 0.5 mm and resistivity of 1.6 x 10-82 m. What will be the length of this wire to make its resistance 10 2? How much does the resistance change if the diameter is doubled?
( āϤাāĻŽā§° āϤাঁā§°ā§° āĻŦ্āϝাāϏ ā§Ļ.ā§Ģ āĻŽিāĻŽি āĻā§°ু āĻĒ্ā§°āϤিā§°োāϧীāϤা ā§§.ā§Ŧ āĻāĻ্āϏ ā§§ā§Ļ-ā§Žā§¨ āĻŽিāĻাā§°। āĻāϝ়াā§° āĻĒ্ā§°āϤিā§°োāϧ ā§§ā§Ļ ⧍ āĻā§°িāĻŦāϞৈ āĻāĻ āϤাঁā§°ā§° āĻĻৈā§°্āĻ্āϝ āĻিāĻŽাāύ āĻš'āĻŦ? āϝāĻĻি āĻŦ্āϝাāϏ āĻĻুāĻুāĻŖ āĻā§°া āĻšāϝ় āϤেāύ্āϤে āĻĒ্ā§°āϤিā§°োāϧ āĻিāĻŽাāύ āĻĒā§°িā§ąā§°্āϤāύ āĻšāϝ়? )
Answer:-
7. The values of current I flowing in a given resistor for the corresponding values of potential difference Vacross the resistor are given below -
( āϏāĻŽ্āĻাā§ą্āϝ āĻĒাā§°্āĻĨāĻ্āϝ⧰ āϏংāĻļ্āϞিāώ্āĻ āĻŽূāϞ্āϝāĻŦোā§°ā§° āĻŦাāĻŦে āĻŽāĻ āĻĒ্ā§°āĻĻāϤ্āϤ ā§°েāĻিāώ্āĻā§°āϤ āĻĒ্ā§°āĻŦাāĻšিāϤ āĻšোā§ąা āĻŦিāĻĻ্āϝুāϤ⧰ āĻŽূāϞ্āϝāĻŦোā§° āϤāϞāϤ āĻĻিāϝ়া āĻšৈāĻে - )
I(amperes) 0.5 1.0 2.0 3.0 4.0
I(āĻāĻŽ্āĻĒিāϝ়াā§°) ā§Ļ.ā§Ģ ā§§.ā§Ļ ⧍.ā§Ļ ā§Š.ā§Ļ ā§Ē.ā§Ļ
V (volts) 1.6 3.4 6.7 10.2 13.2
V (āĻāϞ্āĻ) ā§§.ā§Ŧ ā§Š.ā§Ē ā§Ŧ.ā§ ā§§ā§Ļ.⧍ ā§§ā§Š.⧍
Plot a graph between V and I and calculate the resistance of that resistor.
Answer:-
8. When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
( āϝেāϤিāϝ়া āĻāĻা ⧧⧍ āĻি āĻŦেāĻাā§°ী āĻ āĻ্āĻাāϤ ā§°েāĻিāώ্āĻā§°ā§° āĻāĻĒā§°েā§°ে āϏংāϝোāĻিāϤ āĻšāϝ়, āĻŦā§°্āϤāύীāĻোāϤ ⧍.ā§Ģ āĻāĻŽāĻ āĻŦিāĻĻ্āϝুā§ āĻĨাāĻে। āĻĒ্ā§°āϤিā§°োāϧāĻাā§°ীā§° āĻĒ্ā§°āϤিā§°োāϧ⧰ āĻŽূāϞ্āϝ āύিā§°্āĻŖāϝ় āĻā§°āĻ। )
Answer:-
9. A battery of 9 V is connected in series with resistors of 0.2 02, 0.3 0, 0.42, 0.52 and 12, respectively. How much current would flow through the 12 resistor?
( ⧝ āĻি-ā§° āĻāĻা āĻŦেāĻাā§°ী āĻ্ā§°āĻŽাāύ্āĻŦāϝ়ে ā§Ļ.⧍ ā§Ļ⧍, ā§Ļ.ā§Š ā§Ļ, ā§Ļ.ā§Ē⧍, ā§Ļ.ā§Ģ⧍ āĻā§°ু ⧧⧍ ā§° ā§°েāĻিāώ্āĻā§°ā§° āϏৈāϤে āĻļৃংāĻāϞাāϤ āϏংāϝোāĻিāϤ āĻšāϝ়। ⧧⧍ ā§°েāĻিāώ্āĻā§°ā§° āĻŽাāĻেā§°ে āĻিāĻŽাāύ āĻŦিāĻĻ্āϝুā§ āĻĒ্ā§°āĻŦাāĻšিāϤ āĻš'āĻŦ? )
Answer:-
10. How many 176 Q resistors (in parallel) are required to carry 5 A on a 220 V line?
( ⧍⧍ā§Ļ āĻি āϞাāĻāύāϤ ā§Ģ āĻ āĻ āĻĸ়িāĻŦāϞৈ āĻিāĻŽাāύāĻা ā§§ā§ā§Ŧ āĻিāĻ ā§°েāĻিāώ্āĻā§° (āϏāĻŽাāύ্āϤ⧰াāϞāĻাā§ąে) āĻĒ্ā§°āϝ়োāĻāύ? )
Answer:-
11. Show how you would connect three resistors, each of resistance 6 so that the combination has a resistance of (i) 9 , (ii) 4 .
( āĻāĻĒুāύি āϤিāύিāĻা ā§°েāĻিāώ্āĻā§° āĻেāύেāĻĻā§°ে āϏংāϝোāĻ āĻā§°িāĻŦ āĻĻেāĻুā§ąাāĻāĻ, āĻĒ্ā§°āϤিāĻো āĻĒ্ā§°āϤিā§°োāϧ ā§Ŧ āϝাāϤে āĻŽিāĻļ্ā§°āĻŖāĻোāϤ (āĻ) ⧝, (āĻāĻāĻāĻ) ā§Ē ā§° āĻĒ্ā§°āϤিā§°োāϧ āĻĨাāĻে। )
Answer:-
12. Several electric bulbs designed to be used on a 220 V electric
( ⧍⧍ā§Ļ āĻি āĻŦৈāĻĻ্āϝুāϤিāĻ āϤ āĻŦ্āĻ¯ā§ąāĻšাā§° āĻā§°িāĻŦāϞৈ āĻĄিāĻাāĻāύ āĻā§°া āĻেāĻāĻŦাāĻাāĻ āĻŦৈāĻĻ্āϝুāϤিāĻ āĻŦাāϞ্āĻŦ )
Answer:-
13. A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ί resistance, which may be used separately, in series, or in parallel. What are the corrrents in the three case?
( ⧍⧍ā§Ļ āĻি āϞাāĻāύ⧰ āϏৈāϤে āϏংāϝোāĻিāϤ āĻŦৈāĻĻ্āϝুāϤিāĻ āĻ
āĻেāύ⧰ āĻāĻা āĻā§°āĻŽ āĻĒ্āϞেāĻāϤ āĻĻুāĻা āĻĒ্ā§°āϤিā§°োāϧ āĻুāĻŖ্āĻĄāϞী āĻ āĻā§°ু āĻŦি āĻĨাāĻে, āĻĒ্ā§°āϤিāĻোāϤ ⧍ā§Ē Ί āĻĒ্ā§°āϤিā§°োāϧ āĻĨাāĻে, āϝাāĻ āĻĒৃāĻĨāĻে, āĻļৃংāĻāϞাāϤ āĻŦা āϏāĻŽাāύ্āϤ⧰াāϞāĻাā§ąে āĻŦ্āĻ¯ā§ąāĻšাā§° āĻā§°া āĻš'āĻŦ āĻĒাā§°ে। āϤিāύিāĻা āĻ্āώেāϤ্ā§°āϤ āĻি āĻš'āĻŦ? )
Answer:-
14. Compare the power used in the 2 Ί resistor in each of the following circuits: (i) a 6 V batter in series with 1 Ί and 2 Ί resistors, and (ii) a 4 V battery in parallel with 12 Ί and 2 Ί resistors.
( āύিāĻŽ্āύāϞিāĻিāϤ āĻĒ্ā§°āϤিāĻো āĻŦā§°্āϤāύীāϤ ⧍ Ί ā§°েāĻিāώ্āĻā§°āϤ āĻŦ্āĻ¯ā§ąāĻšৃāϤ āĻļāĻ্āϤি āϤুāϞāύা āĻā§°āĻ: (āĻāĻ) ā§§ Ί āĻā§°ু ⧍ Ί ā§°েāĻিāώ্āĻā§°ā§° āϏৈāϤে āĻļৃংāĻāϞাāϤ ā§Ŧ āĻি āĻŦেāĻাā§°, āĻā§°ু (āĻāĻāĻāĻ) ⧧⧍ Ί āĻā§°ু ⧍ Ί ā§°েāĻিāώ্āĻā§°ā§° āϏāĻŽাāύ্āϤ⧰াāϞāĻাā§ąে ā§Ē āĻি āĻŦেāĻাā§°ী। )
Answer:-
15. Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
( āĻĻুāĻা āϞেāĻŽ্āĻĒ, āĻāĻা ⧍⧍ā§Ļ āĻি-āϤ ā§§ā§Ļā§Ļ āĻĄāĻŦ্āϞিāĻ ā§°েāĻিং, āĻā§°ু āĻāύāĻো ⧍⧍ā§Ļ āĻি-āϤ ā§Ŧā§Ļ āĻĄāĻŦ্āϞিāĻ, āĻŦৈāĻĻ্āϝুāϤিāĻ āĻŽেāĻāύ āϝোāĻাāύ⧰ āϏāĻŽাāύ্āϤ⧰াāϞāĻাā§ąে āϏংāϝোāĻিāϤ। āϝāĻĻি āϝোāĻাāύ āĻāϞ্āĻেāĻ ā§¨ā§¨ā§Ļ āĻি āĻšāϝ় āϤেāύ্āϤে āϞাāĻāύ⧰ āĻĒā§°া āĻি āĻŦিāĻĻ্āϝুā§ āϏংāĻ্ā§°āĻš āĻā§°া āĻšāϝ়? )
Answer:-
16. Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
( āĻোāύে āĻ āϧিāĻ āĻļāĻ্āϤি, 1 āĻāĻŖ্āĻাāϤ 250 āĻĄāĻŦ্āϞিāĻ āĻিāĻি āĻেāĻ, āĻŦা 10 āĻŽিāύিāĻāϤ 1200 āĻĄāĻŦ্āϞিāĻ āĻোāώ্āĻাā§° āĻŦ্āĻ¯ā§ąāĻšাā§° āĻā§°ে? )
Answer:-
17. An electric heater of resistance 8 2 draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
( āĻĒ্ā§°āϤিā§°োāϧ 8 2-ā§° āĻŦৈāĻĻ্āϝুāϤিāĻ āĻšিāĻাā§°ে āϏেā§ąা ā§° āĻŽেāĻāύ⧰ āĻĒā§°া 2 āĻāĻŖ্āĻা15 āĻ āĻা āĻাāύি āĻāύে। āĻšিāĻাā§°āϤ āϤাāĻĒ āĻি āĻšাā§°āϤ āĻŦিāĻāĻļিāϤ āĻšāϝ় āĻāĻŖāύা āĻā§°āĻ। )
Answer:-
18. Explain the following.
( āύিāĻŽ্āύāϞিāĻিāϤāĻŦোā§° āĻŦā§°্āĻŖāύা āĻā§°āĻ। )
(a) Why is the tungsten used almost exclusively for filament of electric lamps?
(āĻ) āĻাংāώ্āĻেāύ āĻĒ্ā§°াāϝ় āĻেā§ąāϞ āĻŦৈāĻĻ্āϝুāϤিāĻ āϞেāĻŽ্āĻĒā§° āĻĢিāϞাāĻŽেāĻŖ্āĻā§° āĻŦাāĻŦে āĻিāϝ় āĻŦ্āĻ¯ā§ąāĻšাā§° āĻā§°া āĻšāϝ়?
Answer:-
(b) Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
(āĻ) āĻŦ্ā§°েāĻĄ-āĻোāώ্āĻাā§° āĻā§°ু āĻŦৈāĻĻ্āϝুāϤিāĻ āϞোāĻšাā§° āĻĻā§°ে āĻŦৈāĻĻ্āϝুāϤিāĻ āĻāϤ্āϤাāĻĒāύ āϝāύ্āϤ্ā§°ā§° āĻĒā§°িāĻŦাāĻšীāĻŦোā§° āĻŦিāĻļুāĻĻ্āϧ āϧাāϤুā§° āĻĒā§°িā§ąā§°্āϤে āĻŽিāĻļ্ā§°āĻŖেā§°ে āĻিāϝ় āϤৈāϝ়াā§° āĻā§°া āĻšāϝ়?
Answer:-
(Ⓒ) Why is the series arrangement not used for domestic circuits?
(Ⓒ) āĻā§°ুā§ąা āĻŦā§°্āϤāύীā§° āĻŦাāĻŦে āĻļৃংāĻāϞা āĻŦ্āĻ¯ā§ąāϏ্āĻĨাāĻো āĻিāϝ় āĻŦ্āĻ¯ā§ąāĻšাā§° āĻā§°া āύāĻšāϝ়?
Answer:-
(d) How does the resistance of a wire vary with its area of cross-section?
(āĻ) āϤাঁā§°ā§° āĻ্ā§°āĻ-āĻেāĻāĻāύ⧰ āĻ্āώেāϤ্ā§°āĻĢāϞ⧰ āϞāĻāϤ ā§°েāĻিāώ্āĻেāύ্āϏ āĻেāύেāĻৈ āϏāϞāύি āĻšāϝ়?
Answer:-
(e) Why are copper and aluminium wires usually employed for electricity transmission?
(āĻ) āĻŦিāĻĻ্āϝুā§ āϏāĻ্āĻাāϞāύ⧰ āĻŦাāĻŦে āϏাāϧাā§°āĻŖāϤে āϤাāĻŽ āĻā§°ু āĻāϞুāĻŽিāύিāϝ়াāĻŽā§° āϤাঁā§° āĻিāϝ় āĻŦ্āĻ¯ā§ąāĻšাā§° āĻā§°া āĻšāϝ়?
Answer:-
Post ID: DABP001788