List of top Science Questions asked in CBSE Class X

Explain with the help of a flow chart that in human beings father is responsible for the sex (male or female) of the child.
Name the compound used in black and white photography. State whether the reaction that occurs is exothermic or endothermic. Give justification for your answer.
Draw the pattern of magnetic field lines due to a current carrying straight conductor. Mark on it the direction of current in the conductor and the direction of the magnetic field developed. Name the rule that helps us to determine the direction of magnetic field lines in this case.
Show the formation of calcium chloride by the transfer of electrons from one element to the other. Atomic Number of calcium and chlorine is 20 and 17 respectively.
"Aluminium oxide is an amphoteric oxide." Justify this statement giving chemical equation for the reactions involved.
Name and describe the most widely used method for refining impure metals?
Assertion (A) : In large animals, oxygen can reach different parts of the animal's body easily.
Reason (R) : Respiratory pigments take up oxygen from the air and carry it to body tissues.
Assertion (A) : White light is dispersed by a glass prism into seven colours.
Reason (R) : The red light bends the least while the violet the most when a beam of white light passes through a glass prism.
In a bisexual flower the male gametes are present in the :
An element 'M' has 25% of the electrons filled in the third shell as in the second shell. The element 'M' is :

Determine the equivalent resistance of the parallel combination of the two resistors (X and Y).

Study the circuit shown in which two resistors X and Y of resistances 3 Ω and 6 Ωrespectively are joined in series with a battery of 2V.

Find the current drawn from the battery by the series combination of the two resistors (X and Y). 

 Study the circuit shown in which two resistors X and Y of resistances 3 Ω and 6 Ω respectively are joined in series with a battery of 2V.

In which combination of resistors will the (i) potential difference across X and Y and (ii) current through X and Y, be the same

Study the circuit shown in which two resistors X and Y of resistances 3 Ω and 6 Ω
respectively are joined in series with a battery of 2V.

Draw a circuit diagram showing the above two resistors X and Y joined in parallel with same battery and same ammeter and voltmeter. 

Name the plant hormone which is synthesized at the shoot tip. How does this hormone help the plant to bend towards light? 

Leaves of the sensitive plant move very quickly in response to ‘touch’. How is this stimulus of touch communicated and explain how the movement takes place? 

Write the name of a hormone that plays a major role in (i) falling of leaves (ii) rapid cell division. 

Name the movement which causes ‘X’ and ‘Y’ to grow downwards and upwards respectively. (Refer above figure)

What is stainless steel? How is it prepared? Write one important property which makes it more useful in making cooking utensils as compared to its primary metal. 

What are alloys? How is ‘Brass’ (an alloy) prepared? 

(I) How does electrical conductivity and melting point of a metal change when it is converted to its alloy by mixing a small amount of an element in it? 

Why can’t two magnetic field lines cross each other? Draw magnetic field lines showing the direction of the magnetic field due to a current-carrying long straight solenoid. State the conclusion which can be drawn from the pattern of magnetic field lines inside the solenoid. 

What are magnetic field lines? How is the direction of the magnetic field at a point determined? Draw the pattern of magnetic field lines of the magnetic field produced by a current-carrying circular loop. 
Mark on it the direction of (i) current and (ii) magnetic field lines. Name the two factors on which the magnitude of the magnetic field due to a current-carrying coil depends.

List any three techniques of contraception used by humans. Which one of these is not meant for males?

Why are testes in human males located outside the abdominal cavity in scrotum?