This question was asked inGPSC AE (Electrical) Class-2 R&B Department Paper 2025 – Series MQuestion 18 of 179 published · Gujarat Public Service CommissionOpen paper
Q120EasySignals & Classification

What is the relation between the unit impulse function and the unit ramp function?

Answer & step-by-step solution
Correct answer: C. δ(t) = d²r(t)/dt²
Quick explanation

The unit ramp r(t) differentiates to the unit step u(t), and differentiating once more gives the unit impulse δ(t). Therefore δ(t) = d²r(t)/dt².

r(t) = t u(t) dr(t)/dt = u(t) d²r(t)/dt² = δ(t)

Concept & Reasoning

The basic continuous-time singularity chain is obtained by integration/differentiation. Starting from δ(t), integration gives u(t); integrating u(t) gives r(t) = t u(t). Reversing the chain, dr/dt = u(t) and du/dt = δ(t). Hence the second derivative of the ramp is the impulse. This is understood in the generalized/distribution sense at t = 0.

How to Solve It in the Exam

Ramp → derivative → step → derivative → impulse.

Important Exam Point

Remember the derivative chain rather than memorizing isolated formulas.

Quick Trick

Ramp → derivative → step → derivative → impulse.

Common Mistake

The impulse is not the first derivative of the ramp; that derivative is the step.

Solution diagram – What is the relation between the unit impulse function and the unit ramp…
Exam tipRemember the derivative chain rather than memorizing isolated formulas.
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