Determine the input voltage source for Example # 5

Statement: An electrical circuit has three resistors which three resistors with two having dropped 5 V and 12 V. A current of 50 mA is flowing through the circuit. Find the value of input source?

1. Using color coding chart, find the value of the resistor, which is 240 ohms in the present case. (Red, Yellow, Brown = 240).

2. Apply Ohm's law to find the voltage across 240 Ω resistor. V = IR = 50 mA * 240 Ω = 12 V.

3. Apply Kirchhoff's Voltage law to find the source voltage:
Source voltage = 5 V + 12 V - 12 V + 3 V = 8 V
So the source is 8 V. You should also know the concept of polarity for solving this problem.


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