A Physics question about cost of energy consume?

2012-03-11 3:02 pm

An electric kettle is required to heat 0.6 litre of water from 10 Celsius to boiling point in 5 min, the supply voltage being 240V. The efficiency of the kettle is 78%. Calculate : a) the resistance of the heating element; b) the cost of energy consumed at 8.0p/kWh. Assume the specific heat capacity of water to be 4190J/kgK and 1 litre of water to have a mass of 1 kg.

I've manage to find the resistance, which is 59.57 ohm, but I don't have any idea on hove to find the second answer (in fact, I didn't saw that unit before! I don't know what that unit means!)

Anyone can help? A hint or a formula would be please...Thanks a lot!!

回答 (1)

[匿名]

2012-03-11 5:35 pm

✔ 最佳答案

The "p" in "8.0p/kWh" probably stands for "penny" or "pence" as in 1/100 of a British pound. Worth about $0.0157 USD.

Since you had to calculate the amount of kWh needed to heat the water, you just multiply it by the rate (8.0p/kWh). Then convert it to whatever currency you want if you need to.

參考: http://www.xe.com/currency/gbp-british-pound http://en.wikipedia.org/wiki/Pound_sterling#Decimal_coinage

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