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Physics Assertion (A) & Reason (B) MCQ

MODEL PAPER 1 · Gujarat Board (GSEB) STD 12 Science (GSEB - English Medium). 4 questions.

Questions

Assertion (A) & Reason (B) MCQ

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4 questions · self-marked practice — reveal the answer and mark yourself.

MCQ 11 Mark
Assertion (A) :A step-up transformer cannot be used as a step-down transformer.
Reason (R): A transformer works only in one direction.
  • A
    Both A and R are true and R is the correct explanation of A
  • B
    Both A and R are true but R is not the correct explanation of A.Empty
  • C
    A is true but R is false.
  • D
    A is false but R is true
Answer
(b) :Both A and R are true but R is not the correct explanation of A.
Explanation: Step-up transformer cannot be used as a step down transformer or vice versa. The assertion is true. So, the transformer is a uni-directional device. The reason is also true. But the reason does not explain the assertion.
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MCQ 21 Mark
Assertion (A) : Light added to light can produce darkness.
Reason (B) : When two coherent light waves interfere, there is darkness at position of destructive interference.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A
  • C
    A is true but R is false.
  • D
    A is false but R is trueEmpty
Answer
(a) : Both A and R are true and R is the correct explanation of A.
Explanation: Both A and R are true and R is the correct explanation of A.
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MCQ 31 Mark
Assertion : For a charged particle moving from point P to point Q, the net work done by an electrostatic field on the particle is independent of the path connecting point P to point Q.
Reason : The net work done by a conservative force on an object moving along a closed loop is zero.
Answer
(b) :Assertion and reason both are correct statements but reason is not correct explanation for assertion.
Explanation: Work done by conservative force does not depend on the path. The electrostatic force is a conservative force.
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MCQ 41 Mark
Assertion (A): The photoelectrons produced by a monochromatic light beam incident on a metal surface, have a spread in their kinetic energies.
Reason (R): The work function of the metal varies as a function of depth from the surface
Answer
(a) : Both A and R are true and R is the correct explanation of A.
Explanation: Electrons being emitted as photoelectrons have different velocities. Actually, all the electrons do not occupy the same level of energy but they occupy continuous band and levels. So, electrons being knocked off from different levels come out with different energies. The work function is the energy required to pull the electron out of the metal surface. Naturally, electrons on the surface will require less energy to be pulled out hence will have lesser work function as compared with those deep inside the metal.
So, Both A and R are true and R is the correct explanation of A.

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