Tag: physics

Questions Related to physics

Energy-related $CO _2$ accounts for approximately what share of total U.S. human-made greenhouse gases?

physics heat and energy

  1. $20%$

  2. $40%$

  3. $60%$

  4. $80%$

Show answer
Correct Option: D
Explanation:

These emissionsmostly from burning coal, oil, and natural gasaccounted for 82 percent of all U.S. greenhouse gases in 2013.

Temperature of earth's atmosphere in absence of green house gases in it:

physics heat and energy

  1. remain constant

  2. increased

  3. decreased

  4. none of the above

Show answer
Correct Option: B
Explanation:

The green house gases absorb some of  the radiation (which is reflected by earth, clouds etc.) and the rest is passed into space. Due to that absorbed radiation, earth's atmosphere remains warm. If green house gases would absent, no radiation will stay on earth's atmosphere and temperature of atmosphere will go fall to approx. $-18^{o}C$ which will freeze all the water on earth. 

The most comfortable value for Relative Humidity is

dew point and humidity heat physics

  1. 10%

  2. 20%

  3. 50%

  4. 90%

Show answer
Correct Option: C
Explanation:

50% 

because in this case it won't be too dry or wont be too wet.

The most comfortable value for RH is ______.

dew point and humidity heat physics

  1. 10%

  2. 30%

  3. 50%

  4. 90%

Show answer
Correct Option: C
Explanation:
The most comfortable of RH is 50%,because of this value many environmental
problems can be reduced which include
Mildew
Mold
Bacteria
Condensation

At dew point. Relative Humidity is

dew point and humidity heat physics

  1. 10%

  2. 20%

  3. 50%

  4. 100%

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Correct Option: D
Explanation:

Dew point is when air gets saturated i.e RH =100%

If RH is high:

dew point and humidity heat physics

  1. we feel sultry

  2. we perspire less

  3. clothes do not dry easily

  4. all the above are correct

Show answer
Correct Option: D
Explanation:
If the air is at 100 percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high.

The units of Relative Humidity are

dew point and humidity heat physics

  1. $kg-m^{3}$

  2. kg

  3. $kg-m^{2}$

  4. none of these

Show answer
Correct Option: D
Explanation:

Relative humidity refers to the ratio of the amount of moisture in the air at a certain temperature to the maximum amount of moisture that the air can retain at the same temperature. Relative humidity is expressed as a percentage and is highest during rain.

Write the correct alternatives :
The vapour content in the air is measured using  a physical quantity called...............

dew point and humidity heat physics

  1. Absolute humidity

  2. Relative humidity

  3. Dew point

  4. Humidity

Show answer
Correct Option: B
Explanation:

Relative humidity :

The ratio of the amount of water vapour actually present in the air to the greatest amount possible at the same temperature.
$\therefore$ option $"B"$ is correct.

When it is raining, the dew point is

dew point and humidity heat physics

  1. $0^\circ C$

  2. $50^\circ C$

  3. $100^\circ C$

  4. room temperature

Show answer
Correct Option: D
Explanation:
When it is raining, the dew point is room temperature.
The dew point is the temperature at which air can hold the amount of mixture present in atmosphere. If the temperature falls below it, some water vapour must condense.

When the room temperature becomes equal to the dew point, the relative humidity of the room is

dew point and humidity heat physics

  1. $100$%

  2. Zero%

  3. $70$%

  4. $85$%

Show answer
Correct Option: A
Explanation:

Relative humidity is the ratio of water vapor pressure and saturation vapor pressure at the present temperature.
When the room temperature becomes equal to the dew point, then the air is saturated. Hence the relative humidity of room is $100$ %.