A full-bridge DC–AC inverter supplies an underdamped RLC load. Which statement best describes the typical waveshapes of the inverter output voltage and the load current?

Introduction / Context:
Voltage-source inverters often generate square or PWM waveforms. When these drive RLC loads, the current response is shaped by the load’s impedance versus frequency, often smoothing toward a sinusoid near resonance or within a narrow band.

Given Data / Assumptions:

• Full-bridge inverter producing a square-wave output voltage.
• Load: underdamped RLC (dominant reactive behavior).

Concept / Approach:
The square voltage has many harmonics. The RLC load presents higher impedance to higher-order harmonics while allowing the fundamental component to pass, producing a current that is nearer to sinusoidal than the voltage. This is the basis for using LC filters with inverters.

Step-by-Step Solution:
1) Decompose the square wave into Fourier components (fundamental plus odd harmonics).2) The RLC impedance magnitude increases away from resonance, attenuating most harmonics.3) The load current thus largely follows the fundamental, becoming nearly sinusoidal.
Verification / Alternative check:
Inverter–filter application notes show square-wave voltage and near-sinusoidal current when the load/filter corner frequency is set appropriately.
Why Other Options Are Wrong:

• Both square: ignores filtering effect.
• Both sinusoidal: contradicts the applied square wave at the inverter terminals.
• Sinusoidal voltage with square current: not applicable for a square-wave inverter.

Common Pitfalls:

• Assuming the current exactly sinusoidal; it is only nearly sinusoidal.
• Neglecting phase shift between voltage and current due to reactance.

Final Answer:
Square voltage, nearly sinusoidal current.