NEET Physics Question - Current Electricity - Relation between Current and Drift Velocity

Assertion (A): The drift speed of electrons in metals is small (in the order of a few \(mm/s\)) and the charge of an electron is also very small (\(= 1.6 \times 10^{-19} C\)), yet we can obtain a large current in a metal.

Reason (R): At room temperature, the thermal speed of electron is very high (about \(10^7\) times the drift speed).

Both (A) & (R) are true and the (R) is the correct explanation of the (A)

Both (A) & (R) are true but the (R) is not the correct explanation of the (A)

(A) is true but (R) is false

Both (A) and (R) are false

Solution:

Assertion is true because metals have a very high density of free electrons (\(n\)). The current is given by \(I = n A v_d e\), and a large \(n\) allows for a large current even with small \(v_d\) and \(e\). Reason is also true as thermal speeds are much higher than drift speeds. However, the high thermal speed does not explain why large currents are obtained.

Rankers Physics

Drift Speed and Current

Solution:

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