gayshipsandcoffee
31.05.2020 •
Physics
A 5.5-kW water heater operates at 240 V.
i. Should the heater circuit have a 20A or a 30A circuit breaker? [2 marks]
ii. Assuming 85% efficiency, how long will the heater take to heat the water in
a 0.2085-m3 tank from 20°C to 80°C? The density of water is 1,000 kg/m3
and the specific heat capacity is 4,200 J/kg/°C.
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Ответ:
The time taken is
Explanation:
From the question we are told
The power the water is
The the voltage of the heater is is
The volume of the heater
The specific heat of water is
The initial temperature is
The final temperature is
The density of water is
The current of the heater is mathematically represented as
substituting values we have
So since the current produced is greater than 20 A hence the heater current rating would be 30A
The quantity of heat required to heat the water is mathematically represented as
Where m is the mass which is mathematically evaluated as
Therefore
Since the heater has an efficiency then the heat generate by the heater is
Now Power is mathematically represented as
Where t is the time taken for heater to heat the water
=>
Substituting values
Ответ:
I believe the answer is: Prices for goods and services increased, and a dollar bought less than it previously had
In the 1970s, united states was experiencing a period of economic stagnation which later known as called the great inflation of the 1970s.
During this period, the number of unemployment skyrocketed and the value of our currency fall dramatically, which caused an increase in overall products and less amount of products it can obtain with previously same amount.