Download App

Atoms — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsAtoms1 Mark
Question
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.

Assertion (A): Electrons in the atom are held due to coulomb forces.

Reason (R): The atom is stable only because the centripetal force due to Coulomb's law is balanced by the centrifugal force.

✓

Answer

  1. A is true, but R is false.

Explanation:

According to postulates of Bohr's atom model, the electron revolve around the nucleus in fixed orbit of definite radii. As long as the electron is In a certain orbits it does not radiate any energy. Not only the centripetal force has to be the centrifugal force, even the stable orbits are fixed by Bohr's theory.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Assertion (A) & Reason (B) MCQ" from Atoms→Atoms — all question types→Physics STD 12 Science question papers→Bihar Board STD 12 Science question papers→Bihar Board question paper generator→

Similar questions

Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): An ammeter is connected in series in the circuit.
Reason (R): An ammeter is a high resistance galvanometer.
→
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion: The electric field and magnetic field have equal average values in linearly polarised plane em wave.
Reason: The electric energy and magnetic energy have equal average values in linearly polarised plane em wave.
→
For question, statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a) (b) (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is NOT the correct explanation of A.
  3. A is true, but R is false.
  4. A is false and R is also false.
Assertion (A): The ratio for time taken for light emission from an atom to that for release of nuclear energy in fission is 1 : 100.
Reason (R): Time taken for the light emission from an atom is of the order of 10-8s.
→
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): The electric flux emanating out and entering a closed surface are 8 × 103 and 2 × 103Vm respectively. The charge enclosed by the surface is $0.053\mu\text{C}.$
Reason (R): Gauss's theorem in electrostatics may be applied to verify.
→
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion: Fuse wire must have high resistance and low melting point.
Reason: Fuse is used for small current flow only.
→
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion: Microscope magnifies the image.
Reason: Angular magnification for image is more than object in microscope.
→
Two statements are given-one labelled Assertion(A) and the other labelled Reason (R). Select the correct answer to these questions from the codes(a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): A compass needle when placed on the magnetic north pole of the earth rotates in vertical direction.
Reason (R): The earth has only horizontal component of its magnetic field at the north poles.
→
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): If a conducting medium is placed between two charges, then electric force between them becomes zero.
Reason (R): Reduction in a force due to introduced material is inversely proportional to its dielectric constant.
→
For two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true, and R is the correct explanation of A.
  2. Both A and R are true, but R is not the correct explanation of A.
  3. A is true, but R is false.
  4. A is false, and R is also false.
Assertion: ln a chain of bulbs, 50 bulbs are joined in series. One bulb is removed now the circuit is again completed. If the remaining 49 bulbs are again connected in series across the same supply, then light gets decreased in the room.
Reason: The resistance of 49 bulbs will be more than 50 bulbs.
→
Two statements are given-one labelled Assertion(A) and the other labelled Reason (R). Select the correct answer to these questions from the codes(a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): At neutral point, a compass needle point out in any arbitrary direction.
Reason (R): Magnetic field of earth is balanced by field due to magnets at the neutral points.
→