Use the circuit diagram to determine the voltage drop across the 8 ω resistor. v

The total resistance in the circuit is (10 + 8 + 6) = 24 ohms.

The current in the circuit is V/R = 12v/24ohms = 0.5 Ampere.

The voltage across the 8-ohm resistor is I·R = (0.5 A) (8ω) = 4 volts.


Another way:

The total resistance in the circuit is 24 ohms.

The total voltage around the circuit is 12 volts.

The voltage divides among the resistors in proportion to each resistance.

The voltage across the 8 ohms is (8/24) of the full 12v = 4 volts.

Similarly, the voltage across the 10 ohms is (10/24) of the full 12v = 5 volts.

And the voltage across the 6 ohms is (6/24) of the full 12v = 3 volts.

Total around the series circuit = (4 + 5 + 3) = 12 volts.   yay!