Class 12 Maths MCQ – Differential Equations

1. A differential equation is an equation that contains:

a) Only derivatives
b) Derivatives and algebraic terms
c) Integral symbols
d) Only algebraic terms

Answer:

b) Derivatives and algebraic terms

Explanation:

A differential equation can contain derivatives, functions of the variable, and constants.

2. The order of the differential equation d^3y/dx^3 = x is:

a) 1
b) 2
c) 3
d) 4

Answer:

c) 3

Explanation:

The order of a differential equation is determined by the highest order derivative present.

3. A differential equation of the form dy/dx = f(x) is called:

a) Ordinary differential equation
b) Partial differential equation
c) Algebraic equation
d) Integral equation

Answer:

a) Ordinary differential equation

Explanation:

It contains derivatives with respect to one variable only, hence ordinary.

4. The general solution of dy/dx = 0 is:

a) y = C
b) y = x + C
c) y = x
d) y = 0

Answer:

a) y = C

Explanation:

The rate of change of y with respect to x is zero, which means y is a constant.

5. The solution of the differential equation d^2y/dx^2 = 0 is:

a) y = C1x + C2
b) y = C
c) y = x^2 + C
d) y = e^x + C

Answer:

a) y = C1x + C2

Explanation:

Integrating once gives dy/dx = C1 and integrating again gives y = C1x + C2.

6. Which method is used to solve dy/dx = y/x?

a) Separation of variables
b) Integrating factor
c) Homogeneous differential equations
d) Bernoulli's equation

Answer:

a) Separation of variables

Explanation:

The variables can be separated to integrate each side individually.

7. The integrating factor of the differential equation dy/dx + Py = Q is:

a) e^∫P dx
b) ∫P dx
c) e^P
d) 1/P

Answer:

a) e^∫P dx

Explanation:

The integrating factor is given by the exponential of the integral of P with respect to x.

8. A first-order, first-degree differential equation is solvable by the method of separable variables if it can be expressed in the form:

a) y' + P(x)y = Q(x)
b) y' = P(y)Q(x)
c) y' = P(x)/Q(y)
d) y' = y + x

Answer:

b) y' = P(y)Q(x)

Explanation:

When it can be expressed as a product of functions of y and x, the variables can be separated.

9. The differential equation representing the family of circles x^2 + y^2 = a^2 is of order:

a) 0
b) 1
c) 2
d) 3

Answer:

b) 1

Explanation:

We need one arbitrary constant (a) to represent this family, so the order is 1.

10. The linear differential equation of the first order is of the form:

a) dy/dx + P(x)y = Q(x)
b) dy/dx = P(x) + y
c) d^2y/dx^2 + P(x)y = Q(x)
d) dy/dx = P(y) + x

Answer:

a) dy/dx + P(x)y = Q(x)

Explanation:

It's a first-order equation where y and its first derivative are in the first degree.

11. A homogeneous differential equation is one which:

a) Has non-constant coefficients
b) Can be reduced to variables separable form
c) Is linear in y and dy/dx
d) Has zero on the right-hand side

Answer:

c) Is linear in y and dy/dx

Explanation:

The term "homogeneous" refers to the degree of terms in the equation being consistent.

12. The solution of dy/dx = y/x with the condition y(1) = 1 is:

a) y = x
b) y = x^2
c) y = e^x
d) y = ln(x)

Answer:

a) y = x

Explanation:

Using separation of variables, we can integrate and apply the boundary condition to find the solution.

13. The differential equation representing the family of lines mx + y = 0 is of order:

a) 0
b) 1
c) 2
d) 3

Answer:

a) 0

Explanation:

We only have one arbitrary constant (m), which means it's a zeroth-order differential equation.

14. A second order differential equation involves:

a) Only the first derivative
b) Up to the second derivative
c) The third derivative
d) No derivatives

Answer:

b) Up to the second derivative

Explanation:

It is based on the highest order of the derivative present.

15. The general solution of d^2y/dx^2 = 9y is:

a) y = C1e^3x + C2e^-3x
b) y = C1cos(3x) + C2sin(3x)
c) y = C1e^3x + C2x e^3x
d) y = C1x^2 + C2x

Answer:

a) y = C1e^3x + C2e^-3x

Explanation:

The given differential equation has constant coefficients, and its characteristic equation gives two real and distinct roots.

16. The differential equation whose solution is y = ae^x + be^-x is of order:

a) 1
b) 2
c) 3
d) 4

Answer:

b) 2

Explanation:

There are two arbitrary constants a and b, so it's a second-order differential equation.

17. If y = e^(mx) is a solution of the differential equation a d^2y/dx^2 + b dy/dx + cy = 0, then m satisfies:

a) am^2 + bm + c = 0
b) am + b = 0
c) am^2 + c = 0
d) bm + c = 0

Answer:

a) am^2 + bm + c = 0

Explanation:

Plugging y = e^(mx) into the differential equation yields the characteristic equation.

18. The solution of the differential equation dy/dx = y^2 is:

a) y = 1/(C-x)
b) y = x + C
c) y = e^(x+C)
d) y = ln|x + C|

Answer:

a) y = 1/(C-x)

Explanation:

Using separation of variables and integrating, we arrive at the solution.

19. The differential equation of all non-vertical lines in a plane is:

a) dy/dx = 0
b) y = x + C
c) dy = dx
d) d^2y/dx^2 = 0

Answer:

d) d^2y/dx^2 = 0

Explanation:

The second derivative is zero for lines, indicating they have constant slope.

20. To find the particular solution of a differential equation, one needs:

a) A general solution
b) An initial or boundary condition
c) A graph of the differential equation
d) The highest and lowest values of y

Answer:

b) An initial or boundary condition

Explanation:

A particular solution is derived from the general solution by applying a specific condition.

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