Explain the role of mouth in digestion o | Class 10 Science Chapter Life Processes, Life Processes 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?

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why?

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

Compare and contrast fossil fuels and the Sun as direct sources of energy.

What are the functions of gastric glands present in the wall of the stomach?

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –

(a) 100 W          (b) 75 W          (c) 50 W          (d) 25 W

In tobacco plant, the male gametes have twenty four chromosomes.
What is the number of chromosomes in the female gamete?
What is the number of chromosomes in the zygote?

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.

Select the mis-matched pair in the following and correct it.
(a) Biomagnification — Accumulation of chemicals at the successive trophic levels of a food chain
(b) Ecosystem — Biotic components of environment
(c) Aquarium — A man-made ecosystem
(d) Parasites — Organisms which obtain food from other living organisms

What are the different ways in which individuals with a particular trait may increase in a population?

A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as

(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw