Name a device that helps to maintain a potential difference across a conductor.

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.

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?

Name the sodium compound which is used for softening hard water.

Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.

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

Find the focal length of a convex mirror whose radius of curvature is 32 cm.

Do basic solutions also have H⁺(aq) ions? If yes, then why are these basic?

Explain the terms analogous and homologous organs with examples.

Find out, from Table 10.3, the medium having highest optical density. Also find the medium with lowest optical density.

     Table 10.3 Absolute refractive index of some material media

How is the equal genetic contribution of male and female parents ensured in the progeny?

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