Class 12 Current Electricity Mock Test (CBSE)

Topics in Current Electricity

• Electric current
• Ohm's law
• Drift of electrons and the origin of resistivity
• Limitations of Ohm's law
• Resistivity of various materials
• Temperature dependence of resistivity
• Electrical energy and power
• Cells, emf and internal resistance
• Cells in series and in parallel
• Kirchhoff's rules
• Wheatstone bridge

Current Electricity practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following statements is correct regarding the electrical resistivity of materials?

   1. (a)Resistivity of typical insulators ranges from $10^{-8} \, \Omega\text{m}$ to $10^{-6} \, \Omega\text{m}$.
   2. (b)Resistivity of alloys like nichrome depends weakly on temperature.
   3. (c)Resistivity of a metallic conductor depends on its cross-sectional area and length.
   4. (d)Resistivity of semiconductors decreases with a decrease in temperature.
   Show answer and step marks

   1. Correct option: (b) Resistivity is an intrinsic property of the material independent of its dimensions, and alloys like nichrome show a weak temperature dependence.+1

   Answer: (b)
2. Q2Multiple choice·1 mark
   The resistivity of a metallic conductor at $0\,^{\circ}\text{C}$ is $\rho_0$ and its temperature coefficient of resistivity is $\alpha$. The fractional change in its resistivity when heated to $T\,^{\circ}\text{C}$ is given by:

   1. (a)$\alpha^2 T$
   2. (b)$\frac{\alpha}{T}$
   3. (c)$1 + \alpha T$
   4. (d)$\alpha T$
   Show answer and step marks

   1. Correct option: (d) Using the relation $\rho = \rho_0(1 + \alpha T)$, the fractional change in resistivity is $\frac{\rho - \rho_0}{\rho_0} = \alpha T$.+1

   Answer: (d)

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