What were the limitations of Döbere | Class 10 Science Chapter Periodic Classification of Element, Periodic Classification of Element 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?

Why are some patients of diabetes treated by giving injections of insulin?

What is the role of the split ring in an electric motor?

How is oxygen and carbon dioxide transported in human beings?

Mention one function for each of these hormones :
(a) Thyroxin
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone.

What is the function of digestive enzymes?

Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?

Why does the sky appear dark instead of blue to an astronaut?

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

Would a Planaria cut vertically into two halves regenerate into two individuals? Complete Figure 8.2 D and E by indicating the regenerated regions.

Why is there a need to harness non-conventional sources of energy? Give two main reasons.