If you are given a Laplace transform F(s) where the degree of the numerator is equal to the degree of the denominator, what is the first step in finding the inverse transform?

Correct answer: Perform long division to separate the function into a constant and a proper rational function.

Explanation

For a Laplace transform F(s) = N(s)/D(s), the technique of partial fraction expansion is only directly applicable if F(s) is a proper rational function, meaning degree(N) < degree(D). If degree(N) >= degree(D), the first step is to perform polynomial long division. This separates F(s) into a polynomial part (whose inverse transform includes impulses and their derivatives) and a proper rational function remainder, which can then be handled with partial fractions.

Other questions

Question 1

In the context of complex frequency, represented as s = σ + jω, what do the real part (σ) and the imaginary part (ω) represent?

Question 2

What are the complex frequencies present in the time-domain function f(t) = 5e^(-7t) cos(80t)?

Question 3

What is the one-sided Laplace transform, F(s), of the unit-impulse function, f(t) = δ(t)?

Question 4

The Laplace transform of a current is I(s) = 5/(s+3). If the initial current i(0-) is 2 A, what is the Laplace transform of its derivative, di/dt?

Question 5

Using the initial-value theorem, find the value of f(0+) for the function whose Laplace transform is F(s) = (3s + 12)/(s^2 + 2s + 10).

Question 6

What is the key condition for applying the final-value theorem to a Laplace transform F(s)?

Question 7

What is the inverse Laplace transform of the function G(s) = (7/s) - 31/(s + 17)?

Question 8

What is the result of applying the initial-value theorem to the transform V(s) = (1/s) + 8/(s+4)?

Question 8

What is the Laplace transform of the time function f(t) = te^(-αt)u(t)?

Question 9

The sifting property of the unit-impulse function is demonstrated by which integral expression?

Question 10

If a function in the time domain, f(t)u(t), is delayed by 'a' seconds, resulting in f(t-a)u(t-a), how does its Laplace transform F(s) change?

Question 11

A function has a Laplace transform F(s) = (2s+4)/s. What is the correct inverse Laplace transform f(t)?

Question 12

What is the complex frequency of a DC voltage V0?

Question 13

In the series RLC circuit from Example 14.1 with R=2 ohms, L=3 H, and C=0.1 F, what is the complex current I if the forcing function is V = 60 at angle 10 degrees and the complex frequency is s = -2 + j4?

Question 14

What is the Laplace transform of the function f(t) = 2u(t - 3)?

Question 15

What is the purpose of the one-sided Laplace transform in circuit analysis?

Question 16

What is the inverse Laplace transform of F(s) = 1/((s + α)(s + β))?

Question 17

How is the Laplace transform of the integral of a function, ∫f(x)dx from 0- to t, related to the function's transform F(s)?

Question 18

What is the inverse Laplace transform of the function P(s) = (7s + 5) / (s^2 + s)?

Question 19

For the series RL circuit in Example 14.7 with R=4 ohms, L=2 H, and an initial current i(0-)=5 A, what is the complete expression for the current i(t) for t > 0 when a 3u(t) V source is applied?

Question 20

What is the Laplace transform of cos(ωt)u(t)?

Question 21

Using the final-value theorem, determine f(infinity) for the transform F(s) = 10 / (s^2 + 3s).

Question 23

In the context of the Laplace transform, what does the linearity theorem state?

Question 24

Find the inverse Laplace transform of V(s) = 2 / (s(s + 6)^2).

Question 25

What is the physical interpretation of a complex frequency s having a positive real part (σ > 0)?

Question 26

What does the Laplace transform pair f(t) <=> F(s) establish between the time domain and the frequency domain?

Question 27

Given a function g(t) = 3[e^(-t) - te^(-2t) - e^(-2t)]u(t), what is its Laplace transform G(s)?

Question 28

What is the Laplace transform of the rectangular pulse defined by v(t) = u(t-2) - u(t-5)?

Question 29

Which property or theorem is most directly used to transform a linear integrodifferential circuit equation from the time domain into an algebraic equation in the s-domain?

Question 30

What is the final value, f(infinity), for a function whose Laplace transform is F(s) = (s^2 + 6)/(s^2 + 7)?

Question 31

A function is defined as f(t) = 2 - 4t + 3.5te^(-10t). What is its Laplace transform H(s)?

Question 32

What are the values of the residues 'a' and 'b' for the partial fraction expansion of P(s) = (7s + 5) / (s(s + 1)) = a/s + b/(s+1)?

Question 33

The Laplace transform of a function is given as I(s) = (0.75/s) + (4.25/(s+2)). What is the value of the function i(t) as t approaches infinity?

Question 34

What is the general form of a real time function that has frequency components at s = -5, s = j8, and s = -j8?

Question 35

The time-domain function for a series RC circuit is u(t) = 4i(t) + v(0-) + 16 ∫i(t')dt' from 0- to t. What is the corresponding s-domain equation?

Question 36

How are the poles of a rational function F(s) = N(s)/D(s) defined?

Question 37

Given H(s) = (2/s) - (4/s^2) + 3.5/((s+10)(s+10)), what is the corresponding time-domain function h(t)?

Question 39

If a function f(t) is multiplied by e^(-at) in the time domain, how does its Laplace transform F(s) change?

Question 40

The Laplace transform of a ramp function, tu(t), is 1/s^2. Using the frequency-shift theorem, what is the transform of f(t) = 5te^(-3t)u(t)?

Question 41

What is the initial value i(0-) of the current in the RL circuit of Example 14.7, as required to solve the problem?

Question 42

A Laplace transform is given by F(s) = 4e^(-2s)(s+50)/s. What is its initial value, f(0+)?

Question 43

The function q(t) has a Laplace transform Q(s) = (11s + 30) / (s^2 + 3s). What is q(t)?

Question 44

What is the result of using the sifting property to evaluate the integral of 4t^2 * δ(t - 1.5) dt from negative to positive infinity?

Question 45

A function V(s) has a simple pole at s = -a, a simple pole at s = -b, and no other poles or zeros. To find its inverse transform v(t), what is the first step in the method of residues?

Question 46

What type of time-domain function corresponds to a Laplace transform with a repeated pole at s=-α, such as F(s) = K/(s+α)^2?

Question 47

For a circuit problem involving a capacitor with an initial voltage v(0-), how is this initial condition incorporated into the s-domain equations using the time integration theorem?

Question 48

Given the function Q(s) = (3s^2 - 4)/s^2, what is the inverse transform q(t)?

Question 49

The Laplace transform for the derivative of a function is given as s^2 * V(s) - s*v(0-) - v'(0-). What derivative is being transformed?

Question 50

A time function is given by the expression (u(t) - e^(-10t))u(t). What is its Laplace transform V(s)?