Exams › NEET › Physics

Assertion: The drift velocity of electrons in a metallic wire decreases if the temperature of the wire is increased. Reason: On increasing temperature, the conductivity of a metallic wire decreases.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If both assertion and reason are true but reason is not the correct explanation of the assertion.
3. If assertion is true but reason is false.
4. If the assertion and reason both are false.

Correct answer: If both assertion and reason are true but reason is not the correct explanation of the assertion.

Solution

In metals, increasing temperature increases lattice vibrations, which reduces relaxation time and hence decreases drift velocity. Conductivity also decreases with temperature, so both statements are true. However, the reason is not the direct explanation of the assertion; the direct cause is the reduction in relaxation time.

Related NEET Physics questions

• For a metallic wire, the ratio (V)/(i) (where, V= applied potential difference and i= current flowing
• In a metallic conductor, electric current is thought to be due to the movement of
• Assertion If the length of the conductor is doubled, the drift velocity will become half of the original value (keeping potential difference unchanged). Reason At constant potential difference, drift velocity is inversely proportional to the length of the conductor.
• The resistance of an iron wire is 10 $\Omega$ and its temperature coefficient of resistance is $5 \times 10^{-3}\,/^\circ\text{C}$. A current of 30 mA is flowing in it at $20^\circ\text{C}$. Keeping the potential difference across its ends constant, if its temperature is increased to $120^\circ\text{C}$, then the current flowing in the wire will be (in mA):
• A steady current of magnitude \(I\) and an AC current of peak value \(I\) are passed through identical resistors for the same time. The ratio of heat produced in the two resistors is:
• Wire of a certain material is stretched slowly be dep10. Its new resistance and specific resistance becomes respectively.

⚔️ Practice NEET Physics free + battle 1v1 →