A bulb is rated at 200 v- 100 w. what is its resistance? Five such bulbs burn for 4 hours. What is the electrical energy consumed? Calculate the cost if the rate is Rs-4.60 per unit
Answers
p = 100w
v = 200 v
I = ??
we know that
p = v*I
100 = 200 *i
i = 1/2 anphere
(2) here we have
no of bulb = 5
time taken = 4hr
therefore ,
p = 5*200*0.5 = 500 w or 1/2 kw
electrical energy comsumed = p*t = 1/2 *4 = 2 kWh
( 3) total cost = 2*4.6 = 9.2 rupees
Question :-
- A bulb is rated at 200 v- 100 w. what is its resistance? Five such bulbs burn for 4 hours. What is the electrical energy consumed? Calculate the cost if the rate is Rs-4.60 per unit ?
Answer :-
- Resistance = 400 ohms
- The total electrical consumed is 2 units .
- The cost of electrical energy is Rs 9.20
Given :-
- Voltage = 220 volts
- Power = 100 watts
To find :-
- what is its resistance?
- What is the electrical energy consumed?
- Calculate the cost if the rate is Rs-4.60 per unit ?
Solution :-
(a) Calculation of Resistance.
Now,
we all know the voltage and power of the bulb.
So, the resistance can be calculated by using the formula :
- P = V²/ R
where,
- P = Power
- V = Voltage
- R = Resistance
Now, putting the values in the above formula we get,
↠ 100= ( 200 ) ² / R
↠100 R = 40000/100
↠R = 400 ohms
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(b) Now, we Calculate of Electrical Energy Consumed.
As we all know that
- E = P × t
↠ E = 100 / 1000 kilowatt
↠ E = 0.1 kilowatt
Time = 4 hours ( given )
So,
Energy Consumed by 1 bulb = 0.1 × 4
↠ 0.4 kilowatt - hours
And,
Energy Consumed by 5 bulbs = 0.4 × 5
↠ 2 kWh
hence, the total electrical consumed is 2 units .
____________________________
(c) Now, we find the cost of electrical energy
↠ Cost of 1 unit of electricity = Rs 4.60
So,
↠ Cost of 2 units of electricity = Rs 4.60 × 2
↠ Rs 9.20
Hence, the cost of electrical energy is Rs 9.20
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