Tag: physics

Questions Related to physics

A bulb of 40W is producing a light of wavelength 620 nm with 80% of eficiency then no of photons emitted by the bulb in 20 sec are 

physics household circuits precaution with the electrical circuit precautions to be taken while dealing with current devices used to protect from shock of electric current

  1. $2 \times (10) ^ {18}$

  2. $10 \times (10) ^ {18}$

  3. $10 \times (10) ^ {21}$

  4. $2 \times (10) ^ {20}$

Show answer
Correct Option: D
Explanation:

Energy of photon emitted by a bulb,

$E=\dfrac{80}{100}\times 40\times 20=640$
Wavelength of light, $\lambda=620nm$
Energy of photons $E'=\dfrac{hc}{\lambda}$
$=3.2\times 10^{-19}J$
$\therefore$ No of photons emitted , $n=\dfrac E{E'}$
$=\dfrac{640}{32\times 10^{-19}}$
$=2\times 10^{20}$

The range of clinical thermometer is $\displaystyle 35^{0}$ to $\displaystyle 43^{0}$

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

The above statement is true.

The typical range of a sub-lingual thermometer for use in humans is from about $35 °C$ to $42 °C$ or $90 °F$ to $110 °F.$

Among the following what should not be done while or before using a clinical thermometer?

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Ensure that before use the mercury level is below $35\ ^0C$.

  2. Wash the thermometer with hot water.

  3. Handle the thermometer with care, as you handle any glass articles.

  4. Don't hold the thermometer by the bulb while reading it.

Show answer
Correct Option: B
Explanation:

(A) The mercury level should be below $35^{o}C$ or $94^{o}F$ , because minimum reading of a clinical thermometer is $35^{o}C$ hence it must be at lowest level to measure the right temperature .

(B) If we wash thermometer with hot water , mercury will expand due to heat given by hot water and will rise to a higher temperature. If the water is very hot , it may result in the damage of thermometer .Hence it must not be done .
(C) It must be handled with care as being made of glass and mercury inside it is poisonous .
(D) If we hold the bulb by our hand , thermometer will take heat from hand and will show a wrong reading hence we should not hold it by bulb 

The range of clinical thermometer is between:

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. $45 ^\circ C$ and $52 ^\circ C$

  2. $25 ^\circ C$ and $32 ^\circ C$

  3. $65 ^\circ C$ and $72 ^\circ C$

  4. $35 ^\circ C$ and $42 ^\circ C$

Show answer
Correct Option: D
Explanation:

The range of clinical thermometer is from $35^{o}C$ or $94^{o}F$  to $42^{o}C$ or$108^{o}F$.

Before using the clinical thermometer mercury level should be below:

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. $ 45 ^\circ C$

  2. $ 35 ^\circ C$

  3. $ 95 ^\circ C$

  4. $ 55 ^\circ C$

Show answer
Correct Option: B
Explanation:

The mercury level should be below $35^{o}C$ or $94^{o}F$, because minimum temperature of human body can not be below $35^{o}C$. Hence, it must be at lowest level to measure the temperature of human body correctly.

__________thermometers include two different metals that are bonded together and expand at different rates as they warm up.

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Liquid in glass

  2. Gas

  3. Bimetallic strip

  4. Resistance

Show answer
Correct Option: C
Explanation:

Bimetallic thermometer include two different metals , bonded together . These two metals have different coefficients of thermal expansion , due to this they expand or contract at different rates , when put into a temperature change together .This is the principle of a bimetallic thermometer .

 Water cannot be used as a liquid in a thermometer because it has:

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. higher freezing point and lower boiling point than other thermometric liquids

  2. lower freezing point and higher boiling point than other thermometric liquids

  3. low specific heat capacity

  4. transparent colour

Show answer
Correct Option: A
Explanation:

Water cannot be used in thermometer because of its higher freezing point and lower boiling point than other liquids .  If water is used in a thermometer , it will start phase change at $0^{o}C$ and $100^{o}C$ and will not measure temperature , out of this range . This range is very small as compared  to other liquids as mercury , having freezing point about $-39^{o}C$ and boiling point $356^{o}C$ .

Our body temperature cannot fall below:

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. $37 ^\circ C$

  2. $35 ^\circ C$

  3. $40 ^\circ C$

  4. $42 ^\circ C$

Show answer
Correct Option: B
Explanation:

Our body temperature cannot fall below $35^{o}C$ or $95^{o}F$ , because below this temperature body will suffer hypothermia .

The normal temperature of human body is ____________.

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. $27^oC$

  2. $37^oC$

  3. $47^oC$

  4. $57^oC$

Show answer
Correct Option: B
Explanation:

Normal body temperature varies by person, age, activity, and time of day. The average normal body temperature is generally accepted as $98.6°F (37°C)$.

What does the bulb of a clinical thermometer contain?

physics heat - measurement thermometers application of various thermometric scales different types of thermometers

  1. Water

  2. Mercury

  3. Iron

  4. Zinc

Show answer
Correct Option: B
Explanation:
A clinical thermometer is a thermometer used to measure human body temperature. Most old ones use mercury thermometer. It is accurate and sensitive, because it has a narrow place where the mercury level rises very fast.

These thermometers are used in clinics by doctors, so they are also called a doctor's thermometers or medical thermometers. Most of them show both Celsius scale and Fahrenheit temperature scales. The scale runs from 35 degree Celsius to 42 degree Celsius.

Medical thermometers are cleaned before and after each use, with alcohol.