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Physics Assertion (A) & Reason (B) MCQ

MODEL PAPER 9 · 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): The dc and ac both can be measured by a hot wire instrument.
Reason (R): The hot wire instrument is based on the principle of magnetic effect of current.
  • 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 true.
Answer
(c) A is true but R is false.
Explanation: Both ac and dc produce heat, which is proportional to the square of the current. The reversal of direction of current in ac is immaterial so far as production of heat is concerned.  
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MCQ 21 Mark
Assertion (A): In Young’s double-slit experiment if wavelength of incident monochromatic light is just doubled, number of bright fringe on the screen will increase.
Reason (R): Maximum number of bright fringe on the screen is inversely proportional to the wavelength of light used.
  • 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 true.
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: Positive charge always moves from a higher potential point to a lower potential point.
Reason: Electric potential is a vector quantity.
  • A
    Assertion and reason both are correct statements and reason is correct explanation for assertion.
  • B
    Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  • C
    Assertion is correct statement but reason is wrong statement.
  • D
    Assertion is wrong statement but reason is correct statement.
Answer
(c) Assertion is correct statement but reason is wrong statement.
Explanation: If two points P and Q in an electric field are separated by an infinitesimal distance $\Delta x$ and have a potential difference $\Delta V$ between them, $E =-\frac{\Delta V}{\Delta x}$. Here, negative sign implies that $\vec{E}$ has got a direction opposite to the potential gradient, i.e, in the direction of $\vec{E}$, the potential decreases, i.e, positive charge always moves from a higher potential point to a lower potential point.
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MCQ 41 Mark
Assertion (A): In photoemissive cell inert gas is used.
Reason (R): inert gas in the photoemissive cell gives greater current.
  • 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 true.
Answer
(a) Both A and R are true and R is the correct explanation of A.
Explanation: The photoemissive cell contains two electrodes are enclosed in a glass bulb which may be evacuated or contain an inert gas at low pressure. An inert gas in the cell gives greater current but causes a time lag in the response of the cell to very rapid changes of radiation which may make it unsuitable for some purpose.
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Assertion (A) & Reason (B) MCQ - Physics STD 12 Science Questions - Vidyadip