Tag: physics

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

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

  1. attracts paper

  2. repels paper

  3. remains indifferent to paper

  4. either attracts or repels paper
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. True, True

  2. True, false

  3. False, True

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

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

What do you understand by the static or frictional electricity ?

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

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

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

  1. Attraction

  2. Repulsion

  3. No change

  4. cant say
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. $C _v=\dfrac{f}{2} R$
  2. $C _v=fR$
  3. $C _v=\dfrac{f}{R}$
  4. $C _v=\dfrac{R}{f}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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
                $C _{V}=\frac{d(1/2)fRT}{dT}=\frac{f}{2}R$

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

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?

  1. $1.55\times 10^5$
  2. $0.155\times 10^5$
  3. $1.4\times 10^5$
  4. $1.01\times 10^5$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$B=-V\dfrac{\Delta P}{\Delta V}$
$=V _0\dfrac{(1.165-1.01)\times 10^5}{0.1\ V}$
$=1.55\times 10^5$