Sags
Brownouts or sags
Brownouts or sags
I will assume this is a question on AC power into a building. That is referred to as a brown out.
Brownout
The incoming voltage from the source to the transformer is called primary voltage.
Voltage sags: Temporary decrease in voltage below normal levels. Voltage swells: Temporary increase in voltage above normal levels. Voltage spikes: Quick, sharp increases in voltage. Voltage surges: Sudden increases in voltage lasting longer than spikes. Harmonic distortions: Non-linear loads causing frequency deviations from the main power supply.
Lamps (not 'bulbs' ; we plant bulbs!) will only produce their rated power at their rated voltage. These values are printed on the glass envelope. Reducing the voltage applied to a lamp will, therefore, reduce the power it produces. In fact, there's not a simple, linear, relationship between a lamp's voltage and its power, and this means that even small reductions in voltage will result in large reductions in power.Operating lamps, or any devices, come to than, at lower voltages really has nothing to do with efficiency. Certainly, operating a lamp below its rated voltage will most-certainly NOT result in high efficiency. Efficiency is defined as the ratio of output power to input power and has nothing to do with voltage.
In the electrical trade it is called control voltage. This voltage can be any voltage. In North America the common control voltage is 120 volts.
Reductions of weapons held by multiple nations
This is called Osteoporosis. A frequent condition in women who undergo hormone reductions as they age.
the device oprates on the minimum voltage. in this voltage is called threshold voltage.
This is often called a "voltage drop".