One watt is equivalent to how many joules per second?

One watt is defined as the amount of energy transferred or converted per unit of time, specifically one joule per second. This means that if a device operates at a power level of one watt, it is using or producing energy at the rate of one joule every second. This relationship is crucial in understanding power measurements in various applications, including those that involve lasers like K-Lasers, where energy transfer and the rate at which it occurs can significantly impact treatment efficacy. Therefore, stating that one watt is equivalent to one joule per second emphasizes the direct connection between power and energy over time in a clear and precise manner.