List of top Questions asked in CBSE Class X

The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below -
I (amperes) 0.51.02.03.04.0
V (volts)1.63.4  6.710.213.2
Plot a graph between V and I and calculate the resistance of that resistor.

The following table shows the ages of tha year:  

Age (in years) 

5 - 15

15 - 25

25 - 35

35 - 45

45 - 55

55 - 65

Number of patients

6

11

21

23

14

5

Find the mode and the mean of the data given above. Compare and interpret the two measures of central tendency.

Explain the following.
  1. Why is the tungsten used almost exclusively for filament of electric lamps?
  2. Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
  3. Why is the series arrangement not used for domestic circuits?
  4. How does the resistance of a wire vary with its area of cross-section?
  5. Why are copper and aluminium wires usually employed for electricity transmission?
Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?
If all the waste we generate is biodegradable, will this have no impact on the environment?
What are the problems caused by the non biodegradable wastes that we generate?
An electric heater of resistance 8 Ω draws 15 A from the service mains 2 hours. Calculate the rate at which heat is developed in the heater.
Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?
Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
Compare the power used in the 2 Ω resistor in each of the following circuits:
  1. a 6 V battery in series with 1 Ω and 2 Ω resistors,
  2. a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
Why does the sky appear dark instead of blue to an astronaut?
Explain why the planets do not twinkle?
Why do stars twinkle?
What happens to the image distance in the eye when we increase the distance of an object from the eye?
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct this defect? Assume that the near point of the normal eye is 25 cm.
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.
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
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
What could be the reasons for adopting contraceptive methods?

Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

How does reproduction help in providing stability to populations of species?
A person needs a lens of power −5.5 diopters for correcting his distant vision. For correcting his near vision, he needs a lens of power +1.5 diopter. What is the focal length of the lens required for correcting?
(i) distant vision, and
(ii) near vision?