Series DC Circuits Practice Worksheet with Answers

This is a very fundamental concept that students must learn: how to determine the total voltage in a series circuit where opposing voltage sources exist. One thing mistake students sometimes make is to try to discern polarity by looking at the polarity signs at the end terminals of the end battery; i.e. at the 3-volt battery’s left-hand terminal, and the 4.5-volt battery’s right-hand terminal, then try to transfer those signs down to the load terminals. This is not an accurate way to tell polarity, but it seems to “work” for them in some situations. This problem is one example of a situation where this faulty technique most definitely does not work!

Have your students collectively agree on a procedure they may use to accurate discern series voltage sums and polarities. Guide their discussion, helping them identify principles that are true and valid for all series circuits.

With regard to the safety question, there is more to determining risk of shock than a simple voltage check. It is important for your students to realize this, despite “accepted” thresholds for hazardous voltage and such.

One of the more difficult skills for students to develop is the ability to translate the layout of a real-world circuit into a neat schematic diagram. Developing this skill requires lots of practice.

It is very worthwhile for students to discuss how they solve problems such as these with each other. For those students who have trouble visualizing shapes, a simple hint or “trick” to use when translating schematics to illustrations or visa-versa may be invaluable.

The concept of series (total) resistance, in relation to individual resistances, usually does not present any difficulties to new students. Parallel resistances are a bit trickier, though . . .