CBSE 2023 · Region 4 · Set 2 · Q33 · 5 marks
(i)Define mobility of electrons. Give its SI units.(ii)A steady current flows through a wire AB , as shown in the figure. What happens to the electric field and the drift velocity along the wire ? Justify your answer.
(iii)Consider the circuit shown in the figure. Find the effective resistance of the circuit and the current drawn from the battery.
(i)Define electrical conductivity of a wire. Give its SI unit.(ii)High current is to be drawn safely from ($\displaystyle 1$) a low-voltage battery, and ($\displaystyle 2$) a high-voltage battery. What can you say about the internal resistance of the two batteries?(iii)Calculate the total energy supplied by the batteries to the circuit shown in the figure, in one minute.
(i)
Define mobility of electrons. Give its SI units.
(ii)
A steady current flows through a wire AB , as shown in the figure. What happens to the electric field and the drift velocity along the wire ? Justify your answer.
(iii)
Consider the circuit shown in the figure. Find the effective resistance of the circuit and the current drawn from the battery.
(i)
Define electrical conductivity of a wire. Give its SI unit.
(ii)
High current is to be drawn safely from ($\displaystyle 1$) a low-voltage battery, and ($\displaystyle 2$) a high-voltage battery. What can you say about the internal resistance of the two batteries?
(iii)
Calculate the total energy supplied by the batteries to the circuit shown in the figure, in one minute.
Marking-scheme solution
(i)
Mobility: Mobility is defined as the magnitude of the drift velocity per unit electric field.
\[\text { S.I. Unit: } \frac{m^{2}}{V . s} \text { or } \frac{C . s}{k g}
\] (ii) Both electric field and the drift velocity decreases. Justification:
\[v_{d}=\frac{I}{n e A}
\] As area increases across the wire, drift velocity decreases.
\[v_{d}=\frac{e E}{m} \tau
\] As drift velocity decreases, electric field decreases (since e ,m and \(\displaystyle \tau\) are constant). (iii) From the diagram \(\displaystyle 10 \Omega\) and \(\displaystyle 14 \Omega\) are in series \(\displaystyle \mathrm{R}_{1}=10 \Omega+14 \Omega=24 \Omega 10 \Omega\) and \(\displaystyle 10 \Omega\) are in series \(\displaystyle \mathrm{R}_{2}=10 \Omega+10 \Omega=20 \Omega\)
Current ElectricityDrift of Electrons and the Origin of ResistivityApplylong_answermedium
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