## The attached figure in this blog post shows the (conventional) current through the resistor.

In most cases, a resistor in series will have a lower voltage drop than in parallel with other resistors and therefore be used in series in electrical circuits. The current through a particular resistor is governed by Ohm’s law, which states that the amount of electric charge flowing per second between two points in an electric circuit is directly proportional to the potential difference or electromotive force (EMF) applied across those two points – i.e., I=E/R; where E is expressed in volts and R as resistance in ohms.

The current in a resistor is inversely proportional to the resistance, and in series resistors this means that the total voltage drop across all of them will be less than if they were in parallel. In the attached figure, in a circuit where there is only one resistor in series with an electric power supply or battery and that load draws 50mA of current (a common measurement), then since R=300Ω: I = E/R; I = 12.0V / 300 Ω ≈ 0.04 amps

### And therefore in this case the voltage drop across the resistor would be Vdrop=IR≈12 volts.

In contrast to parallel circuits, in which all resistors carry identical currents, in a series circuit each resistor has its own specific current drawn through it as determined by Ohm’s law – so if in our example above we had two 100kΩ resistors in series with a 12V power supply in which the load drew 50mA: I = E/R; I = 12.0 Volts / (100,000Ω) ≈ 0.0012 amps

And so in this case since R=200k Ω and Vdrop≠0 volts then the voltage drop across each resistor would be Vdrop=IR≈24 volts for total of 48 volts. Note that in both cases if we doubled our current from 50mA to 100 mA there is no change in voltage drop – because doubling the current will also double the resistance in series with it, meaning i x R stays constant at either .04 or .0012 respectively thus keeping their respective voltages unchanged).

### SEO keywords: in the attached figure;

Ohm’s law – so if in our example above we had two 100kΩ resistors in series with a 12V power supply in which the load drew 50mA. in which in this case, since R=200k Ω and Vdrop≠0 volts then the voltage drop across each resistor would be Vdrop=IR≈24 volts for total of 48 volts.

### Number: N/A

Bullet Point – in both cases if we doubled our current from 50mA to 100 mA there is no change in voltage drop – because doubling the current will also double the resistance in series with it, meaning i x R stays constant at either .04 or .0012 respectively thus keeping their respective voltages unchanged)

- why do I have a headache? (attempting to understand Ohm’s law here…)
- ugh so now what does that mean in terms of power in the circuit?
- and if I want to adjust how much current flows through my resistors, what do I need to do then? (answer: use different sized resistors)

### Bullet Point – in both cases if we doubled our current from 50mA to 100 mA there is no change in voltage drop

why do I have a headache? (attempting to understand Ohm’s law here.) ugh so now what does that mean in terms of power in the circuit? is it a resistor’s voltage or current that might change when they’re in series with each other? and if I want to adjust how much current flows through my resistors, what do I need to do then? (answer: use different sized resistors)

### The Current Through A Resistor: A Closer Look by Brian D. Haines on Tuesday, October 17, 2013

In the attached figure, the (conventional) current through the resistor will go in accordance with Ohm’s law. The power in this circuit is unchanged in both cases if we doubled our current from 50mA to 100 mA there is no change in voltage drop across either resistor and so they each dissipate 20% of their respective powers in heat; however in a parallel configuration where resistors are connected end-to-end as shown below it should be noted that doubling the value of one resistor still results in an identical resistance between its ends which means why do I have a headache? (attempting to understand Ohm’s law here.) ugh so now what does that mean