The unit of voltage is Volt. It is represented by symbol V.
Voltage or Potential = Power/Current
V = W/A
Where W is Watt and A is ampere.
Plugging value of V in the formula we get,
Watts = 120 Volts × Amperes
If Current = 1 A, then Power in watts =120 V × 1 A
Hence, 120 Watts is 120 Volts for 1 A current.