CBSE EXAMINATION PAPER-2025

The students in a class took a thick sheet of cardboard and made a small hole in its centre. Sunlight was allowed to fall on this small hole and they obtained a narrow beam of white light. A glass prism was taken and this white light was allowed to fall on one of its faces. The prism was turned slowly until the light that comes out of the opposite face of the prism appeared on the nearby screen. They studied this beautiful band of light and concluded that it is a spectrum of white light.

Select from the following a hydrocarbon having one C–C bond and one C≡C bond:

Select TRUE statements about lymph from the following :

A. Lymph vessels carry lymph through the body and finally open into larger arteries.

B. Lymph contains some amount of plasma, proteins and blood cells.

C. Lymph contains some amount of plasma, proteins and red blood cells.

D. Lymph vessels carry lymph through the body and finally open into larger veins.

Plants like rose and banana have lost the capacity to produce :

Ina bisexual flower the male gametes are present in the :

To get an image of magnification —1 on a screen using a lens of focal length 20 cm, the object distance must be :

An optical device ‘X’ is placed obliquely in the path of a narrow parallel beam of light. If the emergent beam gets displaced laterally, the device ‘X’ is:

An electric bulb is rated 220 V; 11W. The resistance of its filament when it glows with a power supply of 220 V is :

The minimum number of identical bulbs of rating 4V; 6W, that can work safely with desired brightness, when connected in series with a 240 V mains supply is :

In the food chains given below. Select the most efficient food chain in terms of energy :

Which one of the following gets biomagnified at different levels in a food chain ?

Define oxidation. Identify and name the substance oxidized in the following reaction:

CuO + H₂ → Cu + H₂O

Show the formation of magnesium chloride by electron transfer. Write the name of the cation and anion present in the compound formed. (Atomic Number of Mg = 12, Cl = 17)

Explain with the help of a flow chart that in human beings father is responsible for the sex (male or female) of the child.

How is zinc extracted from its ore? Name the processes involved in the extraction and write chemical equations for the reactions that occur during these processes.

Why do we balance a chemical equation? Name and state the law that suggests the balancing of a chemical equation? Balance the following chemical equation:

Zn + H₃PO₄ → Zn₃(PO₄)₂ + H₂

Design an activity to show that metals are good conductors of heat and have high melting points.

The digestion of food in human alimentary canal is a complex process. State the enzyme/salt present in the following and mention their function in the process of digestion :

(i) Saliva

(ii) Bile Juice

(iii) Pancreatic Juice

State two limitations of electrical impulses in multicellular organisms. Why is chemical communication better than electrical impulses as a means of communication between cells in multicellular organisms?

If we want to obtain a virtual and magnified image of an object by using a concave mirror of focal length 18 cm, where should the object be placed? Use mirror formula to determine the object distance for an image of magnification +2 produced by this mirror to justify your answer.

The electrical resistivity of three materials A, B and C at 20°C is given below:

(i) Classify these materials as conductor, alloy and insulator.

(ii) Give one example of each of these materials and state one use of each material in the design of an electrical appliance say an electric stove or an electric iron.

(i) What is regeneration? Give one example of an organism that shows this process and one organism that does not. Why does regeneration not occur in the latter?

(ii) Water in a pond appears dark green and contains filamentous structures. Name these structures and the method by which they reproduce. Explain the process.

(i)Name the part performing following functions in human male reproductive system :

(a) Carries sperm

(b) Production of male gametes

(c) Whose secretion makes the transport of sperms easier

(d) Provide suitable temperature for sperm formation

(ii) Write any two characteristics of sperms.

(iii) What are surgical contraceptive methods? Give the side effect caused by this procedure.

(i) Draw the pattern of the magnetic field lines for the two parallel straight conductors carrying current of same magnitude ‘I’ in opposite directions as shown. Show the direction of magnetic field at a point O which is equidistant from the two conductors. (Consider that the conductors are inserted normal to the plane of a rectangular cardboard.)

(ii) In our houses we receive A.C. electric power of 220 V. In electric iron or electric heater cables having three wires with insulation of three different colours — red, black and green are used to draw current from the mains.

(a) What are these three different wires called? Name them colourwise.

(b) What is the potential difference between the red wire and the black wire?

(c) What is the role of the wire with green insulation in case of accidental leakage of electric current to the metallic body of an electrical appliance?

(i) By using the given experimental set-up. How can it be shown that:

(a) a force is exerted on the current-carrying B conductor AB when it is At placed in a magnetic field.

(b) the direction of force can be reversed in two ways.

(ii) When will the magnitude of the force be highest?

(iii) State Fleming’s left hand rule.