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Multiple choice 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

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 

  1. $2 \times (10) ^ {18}$
  2. $10 \times (10) ^ {18}$
  3. $10 \times (10) ^ {21}$
  4. $2 \times (10) ^ {20}$
Reveal answer Fill a bubble to check yourself
D Correct answer
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 , $n=\dfrac E{E'}$
$=\dfrac{640}{32\times 10^{-19}}$
$=2\times 10^{20}$

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

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

  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.
Reveal answer Fill a bubble to check yourself
B Correct answer
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 

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

Before using the clinical thermometer mercury level should be below:

  1. $ 45 ^\circ C$
  2. $ 35 ^\circ C$
  3. $ 95 ^\circ C$
  4. $ 55 ^\circ C$
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. Liquid in glass

  2. Gas

  3. Bimetallic strip

  4. Resistance
Reveal answer Fill a bubble to check yourself
C Correct answer
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 .

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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 $356^{o}C$ .

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

What does the bulb of a clinical thermometer contain?

  1. Water

  2. Mercury

  3. Iron

  4. Zinc
Reveal answer Fill a bubble to check yourself
B Correct answer
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.