a bulb is rated at 200v-100w what is it resistance five such bulbs burn for 4 hours what is the electric energy consumed calculate the cost if its rate is 4.50 per unit
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Answers
Answer :-
• Resistance of the bulb is 400 Ω .
• 2 kWh of electrical energy is consumed .
• Required cost is ₹ 9 .
Explanation :-
We have :-
→ Voltage of the bulb (V) = 200 V
→ Power of the bulb (P) = 100 W
→ Time = 4 hrs
→ Cost per unit = ₹ 4.50
______________________________
Firstly, let's calculate the resistance of the bulb .
P = V²/R
⇒ 100 = (200)²/R
⇒ 100R = 40000
⇒ R = 40000/100
⇒ R = 400 Ω
Now, we have to firstly calculate the energy consumed by the bulbs in "kWh" and then we can calculate the required cost .
Energy consumed by five bulbs :-
= Power × Time
= 5(100 × 4)
= 5(400)
= 2000 Wh
= 2 kWh
Required cost :-
= Number of units × Cost
= 2 × 4.5
= ₹ 9
Given :-
A bulb is rated at 200v-100w what is it resistance five such bulbs burn for 4 hours
To Find :-
Cost
Solution :-
We know that
P = V²/R
100 = (200)²/R
100 × R = 200 × 200
R = 200 × 200/100
R = 400 Ω
Now
The Energy of 5 bulbs = Time × Power
Energy = 4 × 5 × 100
Energy = 20 × 100
Energy = 2000 watt hour = 2 kWh
Now
Cost = Rate × Energy
Cost = 4.5 × 2
Cost = 45/5
Cost = 9