Tamil Nadu Board - Class 9 previous year questions (PYQ)

Directions: In the question below, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option:

Assertion (A): If two linear equations represent coincident lines, the system has infinitely many solutions.

Reason (R): Two lines $a_1x + b_1y + c_1 = 0$ and $a_2x + b_2y + c_2 = 0$ coincide when $\frac{a_1}{a_2} = \frac{b_1}{b_2} = \frac{c_1}{c_2}$.

Organic Chemistry: What is the reaction mechanism for esterification involving 'Magnetism and Electromagnetism'?

Organic Chemistry: What is the reaction mechanism for esterification involving 'Early Civilisations (Mesopotamian, Egyptian, Indus, Chinese)'?

Directions: In the question below, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option:

Assertion (A): Electric current in a conductor is treated as a scalar physical quantity.

Reason (R): Although electric current has both magnitude and direction, it does not obey the laws of vector addition.

Directions: In the question below, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option:

Assertion (A): Heavy water ($D_2O$) is utilized as a moderator in thermal nuclear power reactors.

Reason (R): Deuterium nuclei slow down energetic fission neutrons through elastic collisions without substantial parasitic neutron absorption.

Directions: In the question below, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option:

Assertion (A): Terrace farming is widely practiced in hilly and mountainous agro-ecosystems.

Reason (R): Terraces create stepped flat platforms along slopes that significantly reduce the surface velocity of water runoff and prevent topsoil erosion.