An era is a commonly used word for a long period of time. When used in science, for example geology, an era denotes a clearly defined period of time of arbitrary but well-defined length, such as for example the Mesozoic Era from 252 Maâ66 Ma, delimited by a start event and an end event.
As you increase voltage to the muscle describe how it responds to the increased stimulus. As the voltage was increased from threshold to maximum voltage, there was a greater force in the muscle contraction. Once the maximum voltage (2500 mv) was reached, even if there was an increase in voltage, the force of the muscle contraction remained the same.
Your voltage is an average -- the power goes in a sine wave from zero to about +150 volts, back down thru zero to about -150 volts, and repeats this 60 times per second. The average is calculated to be 117.5 volts, Â¬Â± about 7% variation. So from 109 to 125 volts is about the normal range.