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Partial Differential Equations – Mathematics Optional PYQs (2008–2026)

Here are all 86 Partial Differential Equations questions asked in UPSC Mathematics Optional Paper II from 2008 to 2026, arranged under the 4 topics of the official syllabus. Within each topic the latest questions come first.

Each question ends with a code such as [2024/10m/1a] – the year, the marks and the question number in the paper.

Topic-wise weightage graph of Partial Differential Equations, Mathematics Optional Paper II, 2013–2026 vs 2022–2026
Topic-wise weightage of Partial Differential Equations (Paper II) – share of marks, 2013–2026 (white) vs 2022–2026 (black).

5.1] Formulation of PDEs

9 questions

  1. By eliminating the arbitrary functions f and g from z=f(x2−y)+g(x2+y), form partial differential equation. [2023/10m/5a]

  2. It is given that the equation of any cone with vertex at (a,b,c) is f(x−az−c,y−bz−c)=0. Find the differential equation of the cone. [2022/10m/5a]

  3. Obtain the partial differential equation by eliminating arbitrary function f from the equation f(x+y+z,x2+y2+z2)=0. [2021/10m/5a]

  4. Form a partial differential equation by eliminating the arbitrary functions f(x) and g(y) from z=yf(x)+xg(y) and specify its nature (elliptic, hyperbolic or parabolic) in the region x>0, y>0. [2020/10m/5a]

  5. Form a partial differential equation of the family of surfaces given by the following expression : ψ(x2+y2+2z2,y2−2zx)=0. [2019/10m/5a]

  6. Find the partial differential equation of the family of all tangent planes to the ellipsoid : x2+4y2+4z2=4, which are not perpendicular to the xy plane. [2018/10m/5a]

  7. Form a partial differential equation by eliminating the arbitrary functions f and g from z=yf(x)+xg(y). [2013/10m/5a]

  8. Show that the differential equation of all cones which have their vertex at the origin is px+qy=z. Verify that this equation is satisfied by the surface yz+zx+xy=0. [2009/12m/5a]

  9. Form the partial differential equation by eliminating the arbitrary function f given by : f(x2+y2,z−xy)=0. [2009/6m/5b(i)]

5.2] First order PDEs

22 questions

  1. Find the integral surface of the equations dxxz−y=dyyz−x=dz1−z2. [2026/10m/5a]

  2. Find the complete integral of z(p2−q2)=x−y; p≡∂z∂x, q≡∂z∂y. [2025/15m/7a]

  3. Find the characteristics of the partial differential equation p2+q2=2;p≡∂z∂x,q≡∂z∂y and determine the integral surface which passes through x=0, z=y. [2025/15m/8a]

  4. Find the integral surface of the following quasi-linear equation (y−ϕ)∂ϕ∂x+(ϕ−x)∂ϕ∂y=x−y, which passes through the curve ϕ=0, xy=1 and through the circle x+y+ϕ=0, x2+y2+ϕ2=a2. [2024/15m/7a]

  5. Find a complete integral of the partial differential equation p=(z+qy)2 by using Charpit’s method. [2021/15m/8a]

  6. Find the integral surface of the partial differential equation : (x−y)y2∂z∂x+(y−x)x2∂z∂y=(x2+y2)z that contains the curve : xz=a3, y=0 on it. [2020/15m/6a]

  7. Find the solution of the partial differential equation : z=12(p2+q2)+(p−x)(q−y);p≡∂z∂x,q≡∂z∂y which passes through the x-axis. [2020/15m/7a]

  8. Solve the first order quasilinear partial differential equation by the method of characteristics : x∂u∂x+(u−x−y)∂u∂y=x+2y in x>0,−∞<y<∞ with u=1+y on x=1. [2019/15m/6a]

  9. Find the general solution of the partial differential equation : (y3x−2x4)p+(2y4−x3y)q=9z(x3−y3), where p=∂z∂x, q=∂z∂y, and find its integral surface that passes through the curve : x=t, y=t2, z=1. [2018/15m/6a]

  10. Find a complete integral of the partial differential equation 2(pq+yp+qx)+x2+y2=0. [2017/15m/6a]

  11. Find the general equation of surfaces orthogonal to the family of spheres given by x2+y2+z2=cz. [2016/10m/5a]

  12. Find the general integral of the partial differential equation (y+zx)p−(x+yz)q=x2−y2. [2016/10m/5e]

  13. Determine the characteristics of the equation z=p2−q2, and find the integral surface which passes through the parabola 4z+x2=0,y=0. [2016/15m/6a]

  14. Solve the partial differential equation (y2+z2−x2)p−2xyq+2xz=0 where p=∂z∂x and q=∂z∂y. [2015/10m/5a]

  15. Solve for the general solution pcos(x+y)+qsin(x+y)=z, where p=∂z∂x and q=∂z∂y. [2015/15m/6a]

  16. Find the surface which intersects the surfaces of the system z(x+y)=C(3z+1),(C being a constant) orthogonally and which passes through the circle x2+y2=1, z=1. [2013/15m/6b]

  17. Solve the partial differential equation px+qy=3z. [2012/20m/6a]

  18. Solve the PDE (x+2z)∂z∂x+(4zx−y)∂z∂y=2x2+y [2011/12m/5b]

  19. Solve the following partial differential equation zp+yq=x x0(s)=s,y0(s)=1,z0(s)=2s by the method of characteristics. [2010/20m/6a]

  20. Find the integral surface of : x2p+y2q+z2=0 which passes through the curve : xy=x+y, z=1. [2009/6m/5b(ii)]

  21. Find the general solution of the partial differentia. equation (2xy−1)p+(z−2x2)q=2(x−yz) and also find the particular solution which passes through the lines x=1, y=0. [2008/12m/5a]

  22. Find complete and singular integrals of 2xz−px2−2qxy+pq=0 using Charpit’s method. [2008/15m/6b]

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5.3] Second order linear PDEs

33 questions

  1. Reduce the partial differential equation y∂2z∂x2+(x+y)∂2z∂x∂y+x∂2z∂y2=0 to canonical form and hence solve it. [2026/20m/6a]

  2. Solve the partial differential equation (2D2−5DD′+2D′2)z=24(y−x)+sin(y−x) where D≡∂∂x, D′≡∂∂y, z=z(x,y). [2026/15m/7a]

  3. Find the solution of the equation (D2+DD′−2D2)z=ysinx, where D≡∂∂x and D′≡∂∂y. [2025/10m/5a]

  4. Show that if f and g are arbitrary functions of their respective arguments, then u=f(x−kt+iαy)+g(x−kt−iαy), is a solution of ∂2u∂x2+∂2u∂y2=1C2∂2u∂t2, where α2=1−k2C2. [2024/10m/5a]

  5. Solve the partial differential equation ∂∂y(∂ϕ∂x+ϕ)+2x2y(∂ϕ∂x+ϕ)=0 by transforming it to the canonical form. [2024/15m/8a]

  6. Find the surface passing through the two lines z=x=0 and z−1=x−y=0, and satisfying the partial differential equation ∂2z∂x2−4∂2z∂x∂y+4∂2z∂y2=0. [2023/15m/6a]

  7. Reduce the partial differential equation ∂2z∂y2−∂2z∂x∂y+∂z∂x−∂z∂y(1+1x)+zx=0 to canonical form. [2023/15m/8a]

  8. Find the general solution of the partial differential equation (D2+DD′−6D′2)z=x2sin(x+y) where D≡∂∂x and D′≡∂∂y. [2022/15m/7a]

  9. Reduce the following partial differential equation to a canonical form and hence solve it : yuxx+(x+y)uxy+xuyy=0 [2022/15m/8a]

  10. Find the general solution of the partial differential equation (D2−D′2−3D+3D′)z=xy+ex+2y where D≡∂∂x and D′≡∂∂y. [2021/15m/7a]

  11. Form a partial differential equation by eliminating the arbitrary functions f(x) and g(y) from z=yf(x)+xg(y) and specify its nature (elliptic, hyperbolic or parabolic) in the region x>0, y>0. [2020/10m/5a]

  12. Solve the partial differential equation : (D3−2D2D′−DD′2+2D′3)z=e2x+y+sin(x−2y); D≡∂∂x,D′≡∂∂y [2020/10m/5d]

  13. Reduce the following second order partial differential equation to canonical form and find the general solution : ∂2u∂x2−2x∂2u∂x∂y+x2∂2u∂y2=∂u∂y+12x. [2019/20m/7c]

  14. Solve the partial differential equation : (2D2−5DD′+2D′2)z=5sin(2x+y)+24(y−x)+e3x+4y where D≡∂∂x, D′≡∂∂y. [2018/15m/7a]

  15. Solve (D2−2DD′+D′2)z=ex+2y+x3+sin2x, where D≡∂∂x,D′≡∂∂y,D2≡∂2∂x2,D′2≡∂2∂y2. [2017/10m/5a]

  16. Reduce the equation y2∂2z∂x2−2xy∂2z∂x∂y+x2∂2z∂y2=y2x∂z∂x+x2y∂z∂y to canonical form and hence solve it. [2017/15m/7a]

  17. Solve the partial differential equation ∂3z∂x3−2∂3z∂x2∂y−∂3z∂x∂y2+2∂3z∂y3=ex+y [2016/15m/7a]

  18. Solve (D2+DD′−2D′2)u=ex+y, where D=∂∂x and D′=∂∂y. [2015/10m/5b]

  19. Reduce the second-order partial differential equation x2∂2u∂x2−2xy∂2u∂x∂y+y2∂2u∂y2+x∂u∂x+y∂u∂y=0 into canonical form. Hence, find its general solution. [2015/15m/8a]

  20. Solve the partial differential equation (2D2−5DD′+2D′2)z=24(y−x). [2014/10m/5a]

  21. Reduce the equation ∂2z∂x2=x2∂2z∂y2 to canonical form. [2014/15m/6a]

  22. Reduce the equation y∂2z∂x2+(x+y)∂2z∂x∂y+x∂2z∂y2=0 to its canonical form when x≠y. [2013/10m/5b]

  23. Solve (D2+DD′−6D′2)z=x2sin(x+y) where D and D′ denote ∂∂x and ∂∂y. [2013/15m/6a]

  24. Solve the partial differential equation (D−2D′)(D−D′)2z=ex+y. [2012/12m/5a]

  25. Solve the PDE (D2−D′2+D+3D′−2)z=e(x−y)−x2y [2011/12m/5a]

  26. Find the surface satisfying ∂2z∂x2=6x+2 and touching z=x3+y3 along its section by the plane x+y+1=0. [2011/20m/6a]

  27. Solve the PDE (D2−D′)(D−2D′)Z=e2x+y+xy. [2010/12m/5a]

  28. Find the surface satisfying the PDE (D2−2DD′+D′2)Z=0 and the conditions that bZ=y2 when x=0 and aZ=x2 when y=0. [2010/12m/5b]

  29. Reduce the following 2nd order partial differential equation into canonical form and find its general solution xuxx+2x2uxy−ux=0. [2010/20m/6b]

  30. Find the characteristics of : y2r−x2t=0 where r and t have their usual meanings. [2009/15m/6a]

  31. Solve : (D2−DD′−2D′2)z=(2x2+xy−y2)sinxy−cosxy where D and D′ represent ∂∂x and ∂∂y. [2009/15m/6b]

  32. Find general solution of the particle differential equation : (D2+DD′−6D′2)z=ycosx, where D=∂∂x, D′=∂∂y. [2008/12m/5b]

  33. Reduce ∂2z∂x2=x2∂2z∂y2 to canonical form. [2008/15m/6c]

5.4] Wave, heat and Laplace equations

22 questions

  1. Two-dimensional harmonic equation in plane polar coordinates (r,θ) takes the form : ∂2V∂r2+1r∂V∂r+1r2∂2V∂θ2=0 Deduce that it has solutions of the form (Arn+Br−n)e±inθ, where A, B, n are constants. Determine V if it satisfies the two-dimensional harmonic equation in the region 0≤r≤a, 0≤θ≤2π and satisfies the conditions : (i) V remains finite as r→0, (ii) V=∑ncncos(nθ) on r=a. [2026/15m/8a]

  2. Solve ∂2u∂x2+∂2u∂y2=0 for a rectangular plate subject to the boundary conditions u(0,y)=0,u(a,y)=0u(x,0)=0,u(x,b)=f(x) [2025/20m/6a]

  3. Show that the solution of the two-dimensional Laplace’s equation ∂2ϕ(x,y)∂x2+∂2ϕ(x,y)∂y2=0,x∈(−∞,∞),y≥0 subject to the boundary condition ϕ(x,0)=f(x), x∈(−∞,∞), along with ϕ(x,y)→0 for |x|→∞ and y→∞ can be written in the form ϕ(x,y)=yπ∫−∞∞f(ξ)dξy2+(x−ξ)2. [2024/20m/6a]

  4. Solve the partial differential equation a2∂2u∂x2=∂2u∂t2,0<x<L,t>0 subject to the conditions u(0,t)=0,u(L,t)=0,t>0u(x,0)=x,(∂u∂t)t=0=1,0<x<L [2023/20m/7c]

  5. Solve the heat equation ∂u∂t=∂2u∂x2, 0<x<l, t>0 subject to the conditions u(0,t)=u(l,t)=0u(x,0)=x(l−x),0≤x≤l [2022/20m/6a]

  6. Solve the wave equation a2∂2u∂x2=∂2u∂t2,0<x<L,t>0 subject to the conditions u(0,t)=0,u(L,t)=0u(x,0)=14x(L−x),∂u∂t|t=0=0 [2021/20m/6a]

  7. One end of a tightly stretched flexible thin string of length l is fixed at the origin and the other at x=l. It is plucked at x=l3 so that it assumes initially the shape of a triangle of height h in the x–y plane. Find the displacement y at any distance x and at any time t after the string is released from rest. Take, horizontal tensionmass per unit length=c2. [2020/20m/8a]

  8. A thin annulus occupies the region 0<a≤r≤b, 0≤θ≤2π. The faces are insulated. Along the inner edge the temperature is maintained at 0∘, while along the outer edge the temperature is held at T=Kcosθ2, where K is a constant. Determine the temperature distribution in the annulus. [2018/20m/8c]

  9. Let Γ be a closed curve in xy-plane and let S denote the region bounded by the curve Γ. Let ∂2w∂x2+∂2w∂y2=f(x,y)∀(x,y)∈S. If f is prescribed at each point (x,y) of S and w is prescribed on the boundary Γ of S, then prove that any solution w=w(x,y), satisfying these conditions, is unique. [2017/10m/5d]

  10. Given the one-dimensional wave equation ∂2y∂t2=c2∂2y∂x2;t>0, where c2=Tm, T is the constant tension in the string and m is the mass per unit length of the string. (i) Find the appropriate solution of the above wave equation. (ii) Find also the solution under the conditions y(0,t)=0, y(l,t)=0 for all t and [∂y∂t]t=0=0, y(x,0)=asinπxl, 0<x<l, a>0. [2017/20m/8a]

  11. Find the temperature u(x,t) in a bar of silver of length 10 cm and constant cross-section of area 1 cm2. Let density ρ=10.6 g/cm3, thermal conductivity K=1.04 cal/(cm sec ∘C) and specific heat σ=0.056 cal/g ∘C. The bar is perfectly isolated laterally, with ends kept at 0∘C and initial temperature f(x)=sin(0.1πx)∘C. Note that u(x,t) follows the heat equation ut=c2uxx, where c2=K/(ρσ). [2016/20m/8a]

  12. Find the solution of the initial-boundary value problem ut−uxx+u=0,0<x<l,t>0u(0,t)=u(l,t)=0,t≥0u(x,0)=x(l−x),0<x<l [2015/15m/7a]

  13. Find the deflection of a vibrating string (length =π, ends fixed, ∂2u∂t2=∂2u∂x2) corresponding to zero initial velocity and initial deflection f(x)=k(sinx−sin2x) [2014/15m/7a]

  14. Solve ∂2u∂t2=∂2u∂x2, 0<x<1, t>0, given that (i) u(x,0)=0, 0≤x≤1 (ii) ∂u∂t(x,0)=x2, 0≤x≤1 (iii) u(0,t)=u(1,t)=0, for all t [2014/15m/8a]

  15. A tightly stretched string with fixed end points x=0 and x=l is initially at rest in equilibrium position. If it is set vibrating by giving each point a velocity λ⋅x(l−x), find the displacement of the string at any distance x from one end at any time t. [2013/20m/6c]

  16. A string of length l is fixed at its ends. The string from the mid-point is pulled up to a height k and then released from rest. Find the deflection y(x,t) of the vibrating string. [2012/20m/6b]

  17. The edge r=a of a circular plate is kept at temperature f(θ). The plate is insulated so that there is no loss of heat from either surface. Find the temperature distribution in steady state. [2012/20m/7b]

  18. Solve ∂2u∂x2+∂2u∂y2=0,0≤x≤a,0≤y≤b satisfying the boundary conditions u(0,y)=0,u(x,0)=0,u(x,b)=0 ∂u∂x(a,y)=Tsin3πya. [2011/20m/6b]

  19. Obtain temperature distribution y(x,t) in a uniform bar of unit length whose one end is kept at 10∘C and the other end is insulated. Also it is given that y(x,0)=1−x, 0<x<1. [2011/20m/6c]

  20. Solve the following heat equation ut−uxx=0,0<x<2,t>0u(0,t)=u(2,t)=0,t>0u(x,0)=x(2−x),0≤x≤2. [2010/20m/6c]

  21. A tightly stretched string has its ends fixed at x=0 and x=l. At time t=0, the string is given a shape defined by f(x)=μx(l−x), where μ is a constant, and then released. Find the displacement of any point x of the string at time t>0. [2009/30m/6c]

  22. Find the steady state temperature distribution in a thin rectangular plate bounded by the lines x=0, x=a, y=0 and y=b. The edges x=0, x=a and y=0 are kept at temperature zero while the edge y=b is kept at 100∘C. [2008/30m/6a]

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Last updated: 30 October 2026