What are the qualities of an ideal sourc | Class 10 Science Chapter Sources of Energy, Sources of Energy NCERT Solutions

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.

Outline a project which aims to find the dominant coat colour in dogs.

Draw the structure for the following compounds.                

       (i)    Ethanoic acid             (ii)   Bromopentane*
       (iii)  Butanone                   (iv)   Hexanal.

*Are structural isomers possible for bromopentane?

A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?

How is the sex of the child determined in human beings?

(a)  What property do all elements in the same column of the Periodic Table as boron have in common?
(b)  What property do all elements in the same column of the Periodic Table as fluorine have in common?

Calculate the number of electrons constituting one coulomb of charge.

A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?

What is an homologous series? Explain with an example.

Why is variation beneficial to the species but not necessarily for the individual?

Element X forms a chloride with the formula XCl₂, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as

     (a) Na     (b) Mg     (c) AI     (d) Si

What changes can you make in your habits to become more environment-friendly?

Although coal and petroleum are produced by degradatioin of bio-mass, yet we need to conserve them. Why?

The human eye can focus on objects at different distances by adjusting the focal length of the eye lens. This is due to

(a) presbyopia.
(b) accommodation.
(c) near-sightedness.
(d) far-sightedness.

How would these advantages differ from the advantages of using a long-term perspective in managing our resources?

Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)

  (a) mass                  (b) speed
  (c) velocity               (d) momentum

Why should curd and sour substances not be kept in brass and copper vessels?

What are the benefits of using mechanical barriers during sexual act?

What are the differences between the transport of materials in xylem and phloem?

Which of the statements about the reaction below are incorrect?

2PbO(s) + C(s) → 2Pb(s) + CO₂(g)

(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.

       (i) (a) and (b)
       (ii) (a) and (c)
       (iii) (a), (b) and c
       (iv) all