Tag: physics

Questions Related to physics

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 :

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

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

  2. zero

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

  4. $\dfrac{\pi}{6}$

Show answer
Correct Option: A
Explanation:

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

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

Which of the following is not a chemical cell

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

  1. Simple voltaic cell

  2. Leclanche cell

  3. Daniel cell

  4. Solar cell

Show answer
Correct Option: D
Explanation:

Solar cell is a photovoltaic cell, rest are chemical cells.

We use a lactometer to test whether the milk is pure or not. True or false 

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Lactometer is a device use to test the purity of milk by the virtue of specific gravity of cow's milk according to standards.

Lactometer is graduated into how many parts

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

  1. Hundred

  2. thousand

  3. ten

  4. one

Show answer
Correct Option: A
Explanation:

Lactometer is graduated into hundred parts.


Hence, option A is correct.

Milk purity is measured using:

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

  1. Hydrometer

  2. Lactometer

  3. Polarimeter

  4. Spectrometer

Show answer
Correct Option: B
Explanation:

Lactometer is an instrument used for measuring the purity of milk.

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.

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

  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

Show answer
Correct Option: C
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

Complete the following sentence.

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

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

  1. $increases$

  2. $decreases$

  3. $independent$

  4. $can't say$

Show answer
Correct Option: A
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.

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

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

  1. Mass

  2. Volume

  3. Relative density

  4. Temperature

Show answer
Correct Option: C
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.

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

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

  1. Voltmeter

  2. Ammeter

  3. Voltameter

  4. Hydrometer

Show answer
Correct Option: D
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.

The narrow stem in a hydrometer

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

  1. increases its sensitivity.

  2. increases upthrust on it

  3. raises its centre of gravity

  4. increases its size

Show answer
Correct Option: A
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.