Resistance and current

I'm not a current student at any school, but I am learning a new profession, and some of it is a basic understanding of elecrticity. I have some knowledge, but definitely not enough, and I have had to self teach most of what I know using old textbooks that I have found added to some military experience in ths subject. anyways I'm trying to teach myself how to calculate current through resistors, but I'm having trouble setting up and working through word problems. I know this may seem simple to most people on here, and I apologize for that, but sucking at something is the first step at being sorta good at something.

Examples

A 242Ω resistor is in parallel with a 180Ω resistor, and a 240Ω resistor is in series with the combination. A current of 22mA flows through the 242Ω resistor. The current through the 180Ω resistor is __mA.

Two 24Ω resistors are in parallel, and a 43Ω resistor is in series with the combination. When 78V is applied to the three resistors, the voltage drop across the 24Ω resistor is___volts.

• What is your question? If you can't give any more detail than "how to solve these problems", then your question will likely be closed. Tell us what you're having trouble with and be specific please. Oct 24, 2013 at 15:15
• Here is the answer to your first problem (scroll down on the link): forums.mikeholt.com/showthread.php?t=104166. Now you can try to figure out how the other question (which is similar) will work out. Oct 24, 2013 at 15:18

A 242Ω resistor is in parallel with a 180Ω resistor, and a 240Ω resistor is in series with the combination. A current of 22mA flows through the 242Ω resistor. The current through the 180Ω resistor is __mA.

Approaching this step by step, note that you can calculate the voltage across the $242 \Omega$ resistor since you're given the current through it. By Ohm's Law:

$$V_{R_{242}} = 22mA \cdot 242 \Omega$$

Now, you're also given that this resistor is in parallel with a $180\Omega$ resistor so the voltage across this resistor must be identical to the voltage across the $242 \Omega$ resistor.

Thus, and again by Ohm's Law, you can calculate the current through the $180\Omega$ resistor.

Two 24Ω resistors are in parallel, and a 43Ω resistor is in series with the combination. When 78V is applied to the three resistors, the voltage drop across the 24Ω resistor is___volts.

Again, approaching this step by step, the 2 parallel connected $24\Omega$ resistors can be combined into 1 equivalent resistor of resistance

$$R_{EQ} = \dfrac{24 \cdot 24}{24 + 24}$$

Now you can use voltage division to find the voltage across the equivalent resistance:

$$V_{R_{EQ}} = 78V \dfrac{R_{EQ}}{R_{EQ} + 43}$$

Can you take it from here?

• Yes perfect explanation! Thank you for all the help everyone. Oct 24, 2013 at 17:42