An electric bulb is rated 220 V and 100 | Class 10 Science Chapter Electricity, Electricity 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?

What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why?

What were the criteria used by Mendeléev in creating his Periodic Table?

Give any two ways in which non-biodegradable substances would affect the environment.

Name the substance which on treatment with chlorine yields bleaching powder.

What will be the formula and electron dot structure of cyclopentane?

Colonies of yeast fail to multiply in water, but multiply in sugar solution. Give one reason for this.

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.

Besides gallium, which other elements have since been discovered that were left by Mendeléev in his Periodic Table? (any two)

What would be the electron dot structure of carbon dioxide which has the formula CO₂?

Explain how sexual reproduction gives rise to more viable variations than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?