A circuit with four 6-ohm resistors wired in series has 12 volts applied to it.

What current flows through this circuit? Answer is 500 mA

I don't understand the conversions and steps of this book.

Hi

Simply the book uses the formula of ohm's law which states that the voltage across a resistor equals to product of its resistance by the current flowing across it; that is:

Ohm's Law: U = R*I where: U = Voltage of resistor / R = Resistance of the resistor
......................................… = Current across the resistor.

So , to find the current, just divide both sides of the equation by ' R ' to get:

U/R = (R*I)/R

U/R = I So, I = U/R

But in your case, you need first to find the equivalent resistance;

R[Equivalent] = Summation of the resistances for the resistors [ Case of series resistors ]

So, R[Equivalent] = R1 + R2 + R3 + R4 = 6 + 6 + 6 + 6 = 24 ohms

Now applying ohms law for the equivalent resistance to get:

I = U / R[Equivalent]

I = (12 volts ) / (24 ohms) = 0.5 Amperes = 500 mA

Hope that is clear. Good Luck.

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