© examsnet.com
Question : 6
Total: 6
(a) An electric bulb is rated at 200 V 100 W
(b) Calculate the energy consumed by 3 such bulbs if they glow continuously for 10 hours for complete month of November.
(c) Calculate the total cost if the rate is 6.50 per unit.
OR
(a) What is meant by the statement, "The resistance of a conductor is one ohm" ?
(b) Define electric power. Write an expression relating electric power, potential difference and resistance.
(c) How many132 Ω 5 A 220 V
(b) Calculate the energy consumed by 3 such bulbs if they glow continuously for 10 hours for complete month of November.
(c) Calculate the total cost if the rate is 6.50 per unit.
OR
(a) What is meant by the statement, "The resistance of a conductor is one ohm" ?
(b) Define electric power. Write an expression relating electric power, potential difference and resistance.
(c) How many
Solution:
(a) Here, potential difference across the bulb, V = 200 V
Power of the bulb,P = 100 W
AsP =
, R =
=
=
Ω = 400 Ω
(b) Electric energy consumed by 1 bulb in 10 hours for 30 days, i.e.,
W = P t
= 100 W × 10 × 30
= 30000 Wh
Electric energy consumed by 3 bulbs
= 30000 × 3
= 90000 Wh
= 90 kWh
= 90 unit
(c) Cost of 90 units of electric energy
= 90 × 6.50 = ₹ 585 .
OR
(a) Ohm's law states that current flowing through a conductor is directly proportional to the potential difference maintained across the two ends of a conductor at constant temperature and pressure.
Let current flowing through a conductor isI , V
As per Ohm's law,V ∝ I
Thus,
V = I R
HereR
As per the question, the resistance of a conductor is1 ohm
LetV = 1 I = 1 A R = 1 ohm 1 ohm
(b) Electric power is the rate at which work is done or energy is transformed in an electrical circuit.
The formula for electric power is given by:
P = V I
where,
P
V
Power can also be written as
P = I 2 R
P =
The above two expressions are got by using Ohms law, where, voltage, current
and resistance are related by the following relation.
Where,
R
V
(c) Forx 132 Ω
Supply voltage,V = 220 V
Current,I = 5 A
Equivalent resistance of the combination= R
1 ∕ R = x × ( 1 ∕ 132 )
R = 132 ∕ x
From Ohm's law :
132 x = 220 ∕ 5
132 x = 44
132 = 44 x
x = 132 ∕ 44
x = 3
So, answer is 3 resistors.
Power of the bulb,
As
(b) Electric energy consumed by 1 bulb in 10 hours for 30 days, i.e.,
Electric energy consumed by 3 bulbs
(c) Cost of 90 units of electric energy
OR
(a) Ohm's law states that current flowing through a conductor is directly proportional to the potential difference maintained across the two ends of a conductor at constant temperature and pressure.
Let current flowing through a conductor is
As per Ohm's law,
Thus,
Here
As per the question, the resistance of a conductor is
Let
(b) Electric power is the rate at which work is done or energy is transformed in an electrical circuit.
The formula for electric power is given by:
where,
Power can also be written as
The above two expressions are got by using Ohms law, where, voltage, current
and resistance are related by the following relation.
Where,
(c) For
Supply voltage,
Current,
Equivalent resistance of the combination
From Ohm's law :
So, answer is 3 resistors.
© examsnet.com
Go to Question: