An 850 W consumer coffee maker can make 10 cups (1.75 litres) of `80^(@)C` coffee from `20^(@)C` tap water in 10 minutes. What percentage of the electrical energy consumed actually makes it to the coffee?

An 850 W consumer coffee maker can make 10 cups (1.75 litres) of `80^(

1.	An 850 W consumer coffee maker can make 10 cups (1.75 litres) of `80^(@)C` coffee from `20^(@)C` tap water in 10 minutes. What percentage of the electrical energy consumed actually makes it to the coffee?
Answer» The energy needed for heating of water `Q_(out)=mcDeltaT=(1.75kg)(4200J//kg*K)(80-20^(@)C)=441,000J` The, energy consumed by the device (electrical energy) `W_("in")=Pt=(850W)(10"min")(60s//"min")=510,000J` The ratio of these two quantities is the efficiency of the device `eta=Q_("out")//W_("in")=(441,000J)//(510,000J)xx100=86.5%`.

Discussion

No Comment Found

Related InterviewSolutions

Mercury boils at `367^(@)C`. However, mercury thermometers are made such that they can measure temperature up to `500^(@)C`. This is done byA. maintaining vacuum above mercury column in the stem of the thermometerB. filling nitrogen gas at high pressure above the mercury columnC. filling nitrogen gas at low pressure above the mercury levelD. filling oxygen gas at high pressure above the mercury column
We consider the radition emitted by the human body which of the following statements is true?A. The radiation is emiited only during the dayB. The radiation is emitted during the summers and absorbed during the wintersC. The radiation emitted lies in the ultraviolet region and hence is not visibleD. The radiation emitted is in the infrared region
A body of length `1 m` having cross sectional area `0.75 m^(2)` has heat flow through it at the rate of `6000 "Joule"//sec`. Then find the temperature difference if `K = 200 Jm^(-1) K^(-1)`.A. `20^(@)C`B. `40^(@)C`C. `80^(@)C`D. `100^(@)C`
A body cools down from `45^(@)C` to `40^(@)C` in 5 minutes and to `35^(@)` in another 8 minutes. Find the temperature of the surrounding.
The temperature of the body is increased from `-73^(@)C` to `357^(@)C`, the ratio of energy emitted per second isA. `1 : 3`B. `1 : 81`C. `1 : 27`D. `1 : 9`
The energy supply being cut-off, an electric heater element cools down to the temperature of its surrounding, but it will not cool further becauseA. supply is cut offB. it is made of metalC. surroundings are radiatingD. element and surroundings have the same temperature.
The radiation emitted by a star `A` is `1000` times that of the sun. If the surface temperature of the sun and star `A` are `6000 K` and `2000 K` respectively. The ratio of the radii of the star `A` and the sun is:A. `300 : 1`B. `600 : 1`C. `900 : 1`D. `1200 : 1`
A rectangular body has maximum wavelength `lambda_(m)` at `2000 K`. Its corresponding wavelength at `3000 K` will beA. `3/2 lambda_(m)`B. `2/3 lambda_(m)`C. `4/9 lambda_(m)`D. `9/4 lambda_(m)`
Assertion : Coefficient of absorption of radiation of an ideal black body is `1`. Reason : An ideal black body emits radiation of all wavelengths.A. If both assertion and reason are true and reason is the correct explanation of assertionB. If the assertion and reason are true but reason is not the correct explanation of assertion.C. If assertion is true but reason is false.D. If both assertion and reason are false.
By virtue of some internal mechanism, temperature of spherical shell is maintained in steady state which emits radiation like black body while kept in vaccum and isolated from all radiation. If this shell is enveloped by another shell `B` of same radius, still emitted like a black body, find the ratio of temperatures of shell `B` and shell `A` when it was alone:A. `(2)^(1//4)`B. `(3)^(1//4)`C. `(4)^(1//4)`D. None of these

An 850 W consumer coffee maker can make 10 cups (1.75 litres) of `80^(@)C` coffee from `20^(@)C` tap water in 10 minutes. What percentage of the electrical energy consumed actually makes it to the coffee?

Discussion

No Comment Found

Related InterviewSolutions

Reply to Comment