List of top Science Questions asked in CBSE Class X

uniform magnetic field
A uniform magnetic field exists in the plane of paper as shown in the diagram. In this field, an electron (e−) and a positron (p+) enter as shown. The electron and positron experience forces :
How will the image formed by a convex lens be affected, if the upper half of the lens is wrapped with a black paper?
The phenomena of light involved in the formation of a rainbow are:
The colour of light for which the refractive index of glass is minimum is:
The current carrying device which produces a magnetic field similar to that of a bar magnet is:
Assertion (A): Electrons move from lower potential to higher potential in a conductor. Reason (R): A dry cell maintains electric potential difference across the ends of a conductor.
Assertion (A): Some vegetable oils are healthy. Reason (R): Vegetable oils generally have long unsaturated carbon chains.
Assertion (A): Sex of the children will be determined by what they inherit from their mother. Reason (R): Women have XX sex chromosomes.
Assertion (A): Green plants trap only 1% of the energy of sunlight that falls on their leaves. Reason (R): All green plants are the producers in a food chain.
Sometimes while running, athletes suffer from muscle cramps. Why? How is the respiration in this case different from aerobic respiration?
Write the other name given to lymph. State its two functions.
Write the formula and the molecular mass of the third homologue of alcohols. State how the boiling point of an alcohol changes as one moves from lower to higher homologues.
Copper powder is taken in a china dish and heated over a burner.Name the product formed and state its colour. Write the chemical equation for the reaction involved.
Write chemical equation for the chemical reaction which occurs when the aqueous solutions of barium chloride and sodium sulphate react together. Write the symbols of the ions present in the compound precipitated in the reaction.
Identify the organ in the human female reproductive system where the sperm encounters the egg cell. What will happen if it is blocked? Name the technique by which it can be blocked.
“The linear magnification produced by a spherical mirror is +3.”Based on this statement answer the following questions:
(a) What is the type of mirror?
(b) Where is the object located?
(c) List two properties of the image formed (other than the size/magnification).
The filament of an electric lamp draws a current of 0.5 A, which lights for 2 hours. Calculate the charge that flows through the circuit.
Why is the electrolysis of water called a decomposition reaction?
Is the reaction exothermic or endothermic?
Name the gases collected at the anode and cathode.
What is the mass ratio of the gases collected at the anode and cathode?
Differentiate between food chain and food web. In a food chain consisting of deer, grass and tiger, if the population of deer decreases, what will happen to the population of organisms belonging to the first and third trophic levels?
Name a plant growth hormone synthesized at the shoot tip. Explain its effect on the growth of a plant in response to light.
Name the ore of mercury and state the form in which it is found in nature. Write the chemical equations along with the condition required for the reactions involved in the extraction of mercury from its ore.
Mendel crossed pure tall pea plants (TT) with pure short pea plants (tt) and obtained F₁ progeny. When the plants of F₁ progeny were self-pollinated, plants of F2 progeny were obtained.