Assertion (A) & Reason (B) MCQ

MCQ 11 Mark

Assertion (A): Faraday’s laws are consequences of the conservation of energy.
Reason (R): In a purely resistive AC circuit, the current lags behind the emf in phase.

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: Faraday’s laws of electromagnetic induction are consequences of the conservation of energy. It involves only the transformation of energy into electrical energy. In a purely resistive circuit, current and voltage are in the same phase.

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MCQ 21 Mark

Assertion (A): According to Huygen’s principle, no backward wave-front is possible.
Reason (R): Amplitude of secondary wavelet is proportional to $(1+\cos \theta)$ where $\theta$ is the angle between the ray at the point of consideration and the direction of secondary wavelet.

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

(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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MCQ 31 Mark

Assertion : When a capacitor is filled completely with a metallic slab its capacity becomes very large.
Reason : Dielectric constant for metal is zero.

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 and R is also false

Answer

(d) A is false and R is also false
Explanation: A is false and R is also false

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MCQ 41 Mark

Assertion (A): When ultraviolet light is incident on a photocell, its stopping potential is $V _0$ and the maximum kinetic energy of the photoelectrons is $K _{\max }$. When the ultraviolet light is replaced by X-rays, both $V _0$ and $K _{\max }$. increase.
Reason (R): Photoelectrons are emitted with speeds ranging from zero to a maximum value because of the range of frequencies present in the incident light.

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: We know that
$eV _0= K _{\max }= hv -\phi$
where $\phi$ is the work function.
Hence, as v increases (note that the frequency of X -rays is greater than that of $U . V$. rays), both $V _0$ and $K _{\text {max }}$ increase. So, $A$ is true but $R$ is false.

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Physics Assertion (A) & Reason (B) MCQ

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