Tag: physics

Questions Related to physics

Which of the following causes change in air pressure?

physics pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

  1. Height

  2. Season

  3. Temperature

  4. All

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Correct Option: D
Explanation:

it is found that with the change in height, season, temperature etc the barometric height changes, This indicates change in air pressure.

If a comb is rubbed on dry hairs, and then brought near paper pieces, it :

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. attracts paper

  2. repels paper

  3. remains indifferent to paper

  4. either attracts or repels paper

Show answer
Correct Option: A
Explanation:

If we bring small bits of paper near a rubber (or plastic) comb, it is found that the comb does not attract the bits of paper. But if the same comb is first rubbed on dry hairs and then it is brought near the paper pieces, it attracts them.

True or False?
S1: Similar charge attracts each other.
S2: Similar charge repels each other.

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. True, True

  2. True, false

  3. False, True

  4. false, false

Show answer
Correct Option: C
Explanation:

There are 2 types of electrical charges - positive and negative - are said to be opposite types of charge. Consistent with our fundamental principle of charge interaction, a positively charged object will attract a negatively charged object. Oppositely charged objects will exert an attractive influence upon each other. In contrast to the attractive force between two objects with opposite chargess, two objects that are of like charge will repel each other. That is, a positively charged object will exert a repulsive force upon a second positively charged object. This repulsive force will push the two objects apart. Similarly, a negatively charged object will exert a repulsive force upon a second negatively charged object. Objects with like charge repel each other.
Hence, the statement is false.

State whether true or false:

Like charges attract each other.

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Like charges repel each other whereas unlike charges attract each other.

Hence, the correct answer is option B.

State whether true or false:

Unlike charges attract each other.

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Answer is A.

When two like charges are brought closer, they repel and when two unlike charges are brought closer, they attract each other.
Hence, unlike charges attaract each other and the statement is true.

What happens when some charge is placed on a soap bubble?

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. Its radius decreases

  2. Its radius increases

  3. The bubble collapses

  4. None of these

Show answer
Correct Option: B
Explanation:

The radius of soap bublle increases because of outward force acting on the bubble due to charging

What do you understand by the static or frictional electricity ?

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. Discarging of two bodies on rubbing them together is called static or frictional electricity.

  2. Charging of two bodies on rubbing them together is called static or frictional electricity.

  3. Electricity which is static is called static or frictional electricity.

  4. Electricity on high friction bodies is called static or frictional electricity.

Show answer
Correct Option: B
Explanation:

Static electricity is produced when a suitable combination of substances (e.g., glass rod and silk, ebonite rod and cat's skin, sealing wax and wool) are rubbed together and get electrified due to friction.

A negatively charged ebonite rod is brought near the glass rod which has been robbed on silk. State your observation between them

physics electric fields introduction to electrostatic force electric force charging and discharging

  1. Attraction

  2. Repulsion

  3. No change

  4. cant say

Show answer
Correct Option: A
Explanation:

Rubbing the glass rod with the silk makes it lose electrons, so glass rod becomes positively charged. When a negatively charged ebonite rod is brought near the glass rod it attract each other as unlike charges attract each other.

Relation between constant volume specific heat $(C _v)$ and degree of freedom $(f)$ for a gas is ($R$ is gas constant) 

physics solar equipment solar power plant production of electricity from solar energy solar power solar energy and its applications generation of electricity

  1. $C _v=\dfrac{f}{2} R$

  2. $C _v=fR$

  3. $C _v=\dfrac{f}{R}$

  4. $C _v=\dfrac{R}{f}$

Show answer
Correct Option: A
Explanation:

The internal energy of 1 mole of an ideal gas at temperature $T$ , having $f$ degrees of freedom is given by ,

          $U=N _{A}\times(1/2)fk _{B}T=(1/2)fRT$  ......................eq1
where $N _{A}=$Avogadro's number
           $k _{B}=$ Boltzmann's constant
from first law of thermodynamics ,
           $dU=dQ-dW$  ............eq2
At constant volume , $dV=0$ 
hence  $dW=PdV=0$
eq2 becomes , $dU=dQ$
but       $dQ=C _{V}dT$  (for 1 mole of gas)
therefore $dU=C _{V}dT$
or            $C _{V}=dU/dT$
putting the value of $U$ in this equation, we get
                $C _{V}=\frac{d(1/2)fRT}{dT}=\frac{f}{2}R$

Temperature of a gas is $20^o$C and pressure is changed from $1.01\times 10^5$ Pa to $1.165\times 10^5$ Pa. If volume is decreased isothermally by $10\%$. Bulk modulus of gas is?

physics solar equipment solar power plant production of electricity from solar energy solar power solar energy and its applications generation of electricity

  1. $1.55\times 10^5$

  2. $0.155\times 10^5$

  3. $1.4\times 10^5$

  4. $1.01\times 10^5$

Show answer
Correct Option: A
Explanation:
$B=-V\dfrac{\Delta P}{\Delta V}$
$=V _0\dfrac{(1.165-1.01)\times 10^5}{0.1\ V}$
$=1.55\times 10^5$