Tag: physics

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Questions Related to physics

Multiple choice physics magnetic effects of electric current direct current types of current movement of charge

If the instantaneous emf and the instantaneous current equations of an A.C. circuit are respectively 
$e = E _0 sin(\omega t - \pi/6), i = I _0 sin (\omega t + \pi/6)$, then the phase difference between voltage and current is :

  1. $\dfrac{\pi}{3}$

  2. zero

  3. $\dfrac{\pi}{2}$

  4. $\dfrac{\pi}{6}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Phase of current   $\phi _1 = wt +\dfrac{\pi}{6}$

Phase of emf    $\phi _2 = wt-\dfrac{\pi}{6}$
Phase difference   $\Delta \phi = \phi _1-\phi _2$
$\implies \Delta \phi = (wt+\dfrac{\pi}{6})-(wt-\dfrac{\pi}{6}) = \dfrac{\pi}{3}$

Multiple choice physics floating bodies hydrometer and lactometer comparing density - relative density principle of floatation and its applications

When a lactometer is used in a given sample of milk 'A' it floats in the milk such that half of the length of its stem is immersed in the milk. When it  is used in another sample of milk 'B', the length of the stem immersed in the milk is one fourth of the total length. Then which of the following statement(s) is(are) true?
(A) Water content in A is more than that in B.
(B) Density of the sample A is less than the density of the sample B.

  1. A is true, but B is false

  2. A and B are false

  3. A and B are true

  4. A is false but B is true
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

As lactometer sinks less in case of B , we can easily say that the density of sample B is more than that of sample A , hence water content in A would be more as milk is denser than water .


so both statements (A) and (B) are correct .
so option (C) is correct

Multiple choice physics forces in fluids hydrometer and lactometer comparing density - relative density principle of floatation and its applications

Complete the following sentence.

The stem of a hydrometer is made narrow because it _______its sensitivity.

  1. $increases$

  2. $decreases$

  3. $independent$

  4. $can't say$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hydrometer is an instrument used for determining the density of a liquid. It usually consists of a glass float with a long thin stem which is graduated. The glass float is a large hollow bulb which increases the buoyancy so that the hydrometer floats. The narrow stem increases the sensitivity of the hydrometer. The bottom of the hydrometer is made heavier by loading it with lead shots so that it floats vertically.

Multiple choice physics forces in fluids hydrometer and lactometer comparing density - relative density principle of floatation and its applications

A hydrometer is used to measure , which of  the following quantity of a liquid ?

  1. Mass

  2. Volume

  3. Relative density

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

A hydrometer is an instrument used to measure the relative density (or specific gravity) of liquids that is, the ratio of the density of the liquid to the density of water.

Multiple choice physics forces in fluids hydrometer and lactometer comparing density - relative density principle of floatation and its applications

Which is the best instrument for testing the state of charge of car battery ?

  1. Voltmeter

  2. Ammeter

  3. Voltameter

  4. Hydrometer
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A hydrometer is used to test the state of charge of a battery cell. This is performed by measuring the density of the electrolyte, which is accomplished by measuring the specific gravity of the electrolyte. The greater the concentration of sulfuric acid, the more dense the electrolyte becomes.

Multiple choice physics forces in fluids hydrometer and lactometer comparing density - relative density principle of floatation and its applications

The narrow stem in a hydrometer

  1. increases its sensitivity.

  2. increases upthrust on it

  3. raises its centre of gravity

  4. increases its size
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The narrow stem in a hydrometer increases its sensitivity.
The pressure increase with depth, so the lower part is made heavy to withstand high pressure.