Assertion (A) & Reason (B) MCQ

Question 11 Mark

Assertion (A): Transformers are used only in alternating current sources, not in direct current.
Reasons (R): Only a.c. can be stepped up or down by means of transformers.

Answer

(a) Both A and R are true and R is the correct explanation of A.
Explanation: A transformer works on the principle of mutual induction. It can step up or step down a changing current like a.c. and not d.c

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Question 21 Mark

Assertion (A): Skiers use air glasses.
Reason (R): Light reflected by snow is partially polarised.

Answer

(b) Both A and R are true but R is not the correct explanation of A.
Explanation: Both A and R are true but R is not the correct explanation of A.

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Question 31 Mark

Assertion: Two concentric charged inner and outer shell are given. The potential difference between the shells depends on charge of inner shell.
Reason: Potential due to charge of outer shell remains same at every point inside the sphere.

Answer

$(a)$ Assertion and reason both are correct statements and reason is correct explanation for assertion.
Explanation:

$V _{ A }=\frac{1}{4 \pi \varepsilon_0} \frac{Q_1+Q_2}{R_2}$
$V_{ B }=\frac{1}{4 \pi \varepsilon_0}\left(\frac{Q_1}{R_1}+\frac{Q_2}{R_2}\right)$
$V _{ B }- V _{ A }=\frac{1}{4 \pi \varepsilon_0} Q_1\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$

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Question 41 Mark

Assertion (A): The de Broglie wavelength of a molecule varies inversely as the square root of temperature.
Reason (R): The root mean square velocity of the molecule depends on the temperature.

Answer

(a) Both A and R are true and R is the correct explanation of A.
Explanation: $v_{r m s} \propto \sqrt{T}$
$\lambda=\frac{h}{m v} \Rightarrow \lambda \propto \frac{1}{v}$

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Physics Assertion (A) & Reason (B) MCQ

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