Question Bank • QB_SUB_EM_0128 MSQ • 2 Marks

Section 1: Engineering Mathematics

Differential Equations

Subtopic: Linear and non-linear first order Ordinary Differential Equations (ODE)

Question Statement:

Which of the following are second-order linear Partial Differential Equations of parabolic type?

Options:

  • (A) One-dimensional transient heat conduction equation $\frac{\partial u}{\partial t} = \alpha \frac{\partial^2 u}{\partial x^2}$
  • (B) One-dimensional wave equation $\frac{\partial^2 u}{\partial t^2} = c^2 \frac{\partial^2 u}{\partial x^2}$
  • (C) Two-dimensional Laplace equation $\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial y^2} = 0$
  • (D) One-dimensional moisture diffusion equation $\frac{\partial C}{\partial t} = D \frac{\partial^2 C}{\partial x^2}$

Answer Key:

A, D

Step-by-Step Solution & Explanation

For $A u_{xx} + B u_{xt} + C u_{tt} = 0$, discriminant $B^2 - 4AC = 0$ is parabolic. The heat and diffusion equations have $B = 0, C = 0 \implies B^2 - 4AC = 0$ (parabolic). Wave equation is hyperbolic ($B^2 - 4AC > 0$) and Laplace is elliptic ($B^2 - 4AC < 0$).
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