The supply voltage is 60V.
To determine the supply voltage, we need to know about the effective resistance and current across the 7 Ω resistor.
What is the effective resistance?
As these resistors are connected in series, so effective resistance is 4 Ω + 7 Ω + 9 Ω = 20 Ω
What is the current across the 7 Ω resistor?
- From Ohm's law, voltage (V)= current (I) × resistance(R)
- Here, the voltage across the 7 Ω resistor is 21 V.
- So, current= 21 / 7=3A
What is the supply voltage?
- Since, these resistors are connected in series, so the current across all the resistors and supply current are same that is 3A.
- So, the supply voltage= current × effective resistance
= 3 × 20 = 60 V
Thus, we can conclude that the supply voltage is 60V.
Learn more about the ohm's law here:
https://brainly.com/question/14296509
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