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Matter In Our Surroundings
Name and define the commercial unit of energy. Express it in joules. Where is it used?
Or
Define one kilowatt hour. Express it in joules.
The commercial unit of electric energy is kilowatt-hour (kWh).
One kilowatt hour is defined as the electric energy consumed by an appliance of power 1000 watt in one hour.
1 kWh = 1 kW x 1 h
= 1000 W x 1 h
= 1000 Js-1 x 3600 s
1 kWh = 3600000 J
= 3.6 x 106 J
The electrical energy used in households, industries and commercial establishments is expressed in kilowatt hour.
Electrical energy used is expressed in terms of ‘units’ in our monthly bills.
Here 1 unit means 1 kilowatt hour.
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What is the physical state of water at
100 °C
For any substance, why does the temperature remain constant during the change of state ?
Suggest a method to liquify atmospheric gases.
Convert the following temperatures to Kelvin scale.
35°C
Give reason for the following observations.
Naphthalene balls disappear with time without leaving any solid.
Give reason for the following observations.
We can get the smell of perfume sitting several metres away.
What is the physical state of water at
a) 25°C
b)00C
c)1000C
What is the physical state of water at
0°C
What is the physical state of water at
100°C
Give two reasons to justify
Water at room temperature is a liquid.
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