Now that the total resistance is known, the circuit current can be calculated as follows:

ER

IT =

RT

20 V

IT =

2 Ω

I T = 10

A

The voltage drop across R1can be computed as follows:

ER1 = R1 x IT

ER1 = 1Ω X 10 A

ER1 = 10 V

The voltage at point A would be equal to the voltage of V1 minus the voltage drop of R1.

Compute this as follows:

Voltage at point A = V1 - ER1

Voltage at point A = +10 V- 10 V

Voltage at point A = 0 V

To check this result, compute the voltage drop across R2 and subtract this from the voltage

at point A. The result should be the voltage of V2. Compute this as follows:

ER2 = R2 x IT

ER2 = 1Ω x 10 A

ER2 = 10 V

V2 = (voltage at point A) - (ER2)

V2 = (0V) - (10 V)

V2 = -10 V

7-62. It is not necessary that the voltage supplied be equal to create a point of virtual

ground. In Figure 7-13, view (B), V1 supplies +1 volt to the circuit while V2 supplies -10

volts. The total difference in potential is 11 volts. The total resistance of this circuit (R1 +

R2) is 11 ohms. The total current (IT) is 1 ampere. The voltage drop across R1 (ER1 = R1 x

IT) is 1 volt. The voltage drop across R2 (ER2 = R2 x IT) is 10 volts. The voltage at point A

can be computed as follows:

Voltage at point A = V1 - ER1

Voltage at point A = (+1V) - (+1V)

Voltage at point A = 0 V

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