What is the total voltage in a DC series circuit with ER1 = 20V, ER2 = 45V, and ER3 = 57V?

In a DC series circuit, the total voltage is calculated by simply adding the voltages across each component. In this case, you have three voltage sources: ER1, ER2, and ER3, with values of 20V, 45V, and 57V respectively.

To find the total voltage, you would perform the addition as follows:

Total voltage = ER1 + ER2 + ER3
Total voltage = 20V + 45V + 57V
Total voltage = 122V

Thus, the total voltage in the circuit is 122V, making it the correct answer. This reflects the fundamental property of series circuits, where the total voltage is the sum of the individual voltages provided by each source.