S104 student, latest TMA?
The approach looks fine. If you are submitting this as an answer, please note
watts and joules have lower case first letters.
note that there is a space between the number and units and between units.
it is either 's' or 'seconds' not 'secs'
How long would it take a kettle with a 1kW heating element to heat 1 litre of water?
Watts = Joules / second
• Mass of 1 litre of water = 1kg
• 1 kW = 1 k Joule / second or 1000 joules/ second
• 1g of water needs 4.184J to raise the temperature by 1̊ c.
• Water Temperature of 20oC
Heat Required (J) = Mass of water (g) x Change in temperature (0C) x 4.184 (J/0Cg)
• Change in Temperature = 1000C- 200C= 800C
• Heat Required (J) = 1000g x 800C x 4.184(J/0Cg) = 334720J
• Time Taken= 334720J/ 1000J per sec= 334.72s
• or 334.72/ 60 = 5mins 58 secs
Is this correct?
2 answers
An electric kettle is rated 5KW.How much time will it take to boil 15kg of water initially at 15degree celsius ,if it is connected to 230V supply .
4 answers