One gram of coal burning liberates 18 kj of energy . How many kilograms of coal will produce as much energy as an electric bulb of 200w consumed in 10 hours.
Answers
Given, Power of bulb = 200 watt or 200 Joules per second
given Time = 10 Hours
•°• Total power consumed by the electric bulb in 10 Hours = 200 * 10 * 3600 ( because we are given Power consumed by the bulb is 200 Joules in 1 second , Therefore we should convert the given time ( 10 Hours ) into seconds. Since 1 Hr = 60 minute = 60 * 60 seconds )
=> 2000 * 3600
=> 72,00,000 Joules or 7200 KJ ( because 1000 J = 1 KJ
Since 1 gram of coal liberates 18 KJ of energy.
•°• Grams of coal which will liberate 7200 KJ will be:
= 7200 ÷ 18
= 400
Therefore, 400 Gram of coal will produce as much energy as an electric bulb of 200 W for 10 Hours.
Answer:
Given :
Power = 200 W
We know :
Power mean energy consumed per second i.e. J / sec
Energy consumed by bulk in 10 hours = 200 × 60 × 60 × 10J
Energy consumed by bulk in 10 hours in kJ = 200 × 60 × 60 × 10 / 1000 kJ
Energy consumed by bulk in 10 hours in kJ = 200 × 36 kJ
1 g coal burning liberates 18 kJ
Therefore , required gram of coal burning liberates = 200 × 36 / 18 g
Finally , it will liberates 400 grams or 0.4 kg .