Find the focal length of a lens of power – 2.0 D. What type of lens is this?

Draw the structure for the following compounds.                

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

*Are structural isomers possible for bromopentane?

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

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.

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.

What is an homologous series? Explain with an example.

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

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?

Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table.

(a) The elements become less metallic in nature.
(b) The number of valence electrons increases.
(c) The atoms lose their electrons more easily.
(d) The oxides become more acidic.

Find out the source of water in your region/locality. Is water from this source available to all people living in that area?

An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

Calculate the number of electrons constituting one coulomb of charge.

A spherical mirror and a thin spherical lens have each a focal length of –15 cm. The mirror and the lens are likely to be

(a) both concave.
(b) both convex.
(c) the mirror is concave and the lens is convex.
(d) the mirror is convex, but the lens is concave.

What are the limitations of the energy that can be obtained from the oceans?

How can three resistors of resistances 2 Ω, 3 Ω, and 6 Ω be connected to give a total resistance of (a) 4 Ω, (b) 1 Ω?

What is the role of decomposers in the ecosystem?

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

(a) the food is not cooked completely.
(b) the fuel is not burning completely.
(c) the fuel is wet.
(d) the fuel is burning completely.

How does the creation of variations in a species promote survival?