Can a 30 watt (RMS) speaker work with a 5V 2A power supply?
Will this speaker will work with 5V and 2A?


Yes, but the maximum average output power will be less than 30 watts; a 5 volt supply capable of delivering a maximum of 2 amps can only produce 10 watts and, given that your amplifier will have an efficiency around 60%, the maximum power delivered from the 5 volt supply will be about 6 watts.

But it's slightly worse than this if you use a conventional linear amplifier because it can only produce maybe 4 volts peak-to-peak and that, as a sinewave, has an RMS value of 1.414 volts. That RMS voltage across an 8 ohm speaker produces a power of only 0.25 watts.

If you used a bridge amplifier you could achieve maybe 8 volts p-p and that would deliver a sinewave power of 1 watt.