We do not clean ponds or lakes, but an a | Class 10 Science Chapter Our Environment, Our Environment 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?

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Explain the structure and functioning of Human eye. How are we able to see nearby as well as distant objects?

Suggest a few measures for controlling carbon dioxide levels in the atmosphere.

The xylem in plants are responsible for

         (a) transport of water.                   (c) transport of amino acids.
         (b) transport of food.                     (d) transport of oxygen.

How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

What are the necessary conditions for autotrophic nutrition and what are its by-products?

Suggest a few useful ways of utilising waste water.

A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?

Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer.

Why do you think that there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?