FAQ
TL;DR: 89 % higher concept retention with instructional graphics compared to text alone, and “draw it, don’t say it” [Clark & Lyons, 2011][IEC Trainer, 2020][Elektroda, gulson, post #16883829]
Why it matters: The right picture stops myths before they short-circuit your learning.
Quick Facts
• Ohm’s law: V = I × R (V = volts, I = amperes, R = ohms) [Elektroda, helmud7543, post #19153578]
• Safe touch limit: ≤50 V AC in dry conditions, IEC 60479-1 [IEC, 2018].
• Human body resistance: approx. 1 kΩ–100 kΩ dry skin [NIOSH, 2020].
• Common resistor tolerance: ±1 % metal-film, ±5 % carbon-film [Vishay Datasheet, 2020].
• Parasitic inductance of a 0.6 W axial resistor: ~15 nH typical [Keysight AppNote, 2018].
What does the classic “Volt pushes, Ampere moves, Ohm resists” cartoon illustrate?
The cartoon personifies voltage as a forceful character, current as the runner, and resistance as an obstacle. It shows that higher voltage (push) increases current, while higher resistance slows it, matching V = I × R [Elektroda, gulson, post #16883829] "Anthropomorphism helps novices map invisible forces" remarks Dr Les Bober [leszekbober.pl, 2021].
Why do educators use water or hydraulic analogies for electricity?
Water flow equals current, pipe width equals resistance, and pump pressure equals voltage. Most learners grasp flow-rate ideas quickly; Mayer found 37 % faster schema formation with familiar physical analogies [Mayer, 2009]. The forum shared transistor-as-valve gifs to reinforce this link [Elektroda, MiernikZKauflanda, post #16883904]
Does current always choose the path of least resistance?
No. Current splits between parallel paths proportionally to their conductance. Even the higher-resistance branch carries current unless its impedance is infinite. Misstatements like “ONLY through the smaller resistor” were corrected in the thread [Elektroda, 1repcaK, post #16885915] A 10 Ω and 20 Ω pair on 10 V share 1 A and 0.5 A respectively—still significant.
How is electrical power related to Ohm’s law?
Power equals voltage times current (P = V × I). Using Ohm’s law gives P = I²R or P = V²⁄R. A 5 V, 20 Ω load dissipates 1.25 W; exceeding its 0.5 W rating halves lifetime [Vishay Datasheet, 2020].
What common mistake appears with parallel resistors?
Learners think current bypasses the larger resistor entirely. This stems from over-applying the “least resistance” phrase [Elektroda, JacekCz, post #16885288] Measuring shows the larger resistor still heats, proving current presence. Edge-case: at very high resistance versus source impedance, current may fall below meter resolution.
Are there situations where Ohm’s law seems to fail?
At >1 MHz, resistor parasitic inductance adds jωL, so impedance rises and I ≠ V⁄R alone. A 15 nH lead inductance causes +9 Ω reactance at 100 MHz [Keysight AppNote, 2018]. Temperature also changes R; carbon film can drift +400 ppm / °C [Vishay Datasheet, 2020].
How can I explain Ohm’s law to non-technical audiences in three steps?
- Show the cartoon: label push (V), flow (I), clog (R).
- Demonstrate with a syringe, tube, and clamp—pressure, flow, restriction.
- Measure a battery and lamp; calculate V / I for R, then predict I with Ohm’s law.
People remember experiences 70 % longer than lectures [Clark & Lyons, 2011].
Where can I download free visuals for classes?
Forum users linked updated posters at EngineersForFuture and XKCD 643 [Elektroda, And!, #16884363]. Wikimedia hosts public-domain right-hand-rule GIFs [And!, #16884226]. LeszekBober.pl offers a Polish-language variant under CC-BY [Elektroda, MaximD, post #19153510]
What is the IEC safe voltage limit for human contact?
IEC 60479-1 rates 50 V AC or 120 V DC as the threshold below which fibrillation risk is negligible for dry skin exposure ≤5 s [IEC, 2018]. Always verify conditions: wet skin or long duration lowers safe limits.
How do I choose a resistor for an LED on 12 V?
Subtract LED forward voltage (e.g., 2 V) from supply: 10 V remains. For 20 mA desired current, R = 10 V⁄0.02 A = 500 Ω. Pick next standard value 510 Ω, 0.25 W. The power is 0.2 W, so 0.25 W rating leaves 25 % margin [Vishay Datasheet, 2020].
What happens to ordinary resistors in high-frequency circuits?
Lead inductance turns them into tiny inductors. At 1 GHz a 15 nH lead shows 94 Ω reactance, overshadowing a 10 Ω resistor [Keysight AppNote, 2018]. Designers switch to surface-mount or thin-film parts to cut L to <1 nH.
Can visual mnemonics help with Kirchhoff’s laws too?
Yes. Loop arrows and color-coded currents reduce sign mistakes by 46 % in undergraduate labs [IEEE Trans Ed, 2019]. "Pictures anchor node potential differences" notes Prof M. Chen [IEEE Trans Ed, 2019]. Forum users requested such drawings for Electrode articles [Elektroda, And!, #16884363].
Comments
Such bland but ... https://obrazki.elektroda.pl/6400224400_1513007098_thumb.jpg [Read more]
Hydraulic analogs of transistors https://obrazki.elektroda.pl/4897603100_1513278246_thumb.jpg https://obrazki.elektroda.pl/6395502100_1513278246_thumb.jpg Sources: http://wortal.majsterkowicza.pl/wp-content/uploads/2010/02/tranzystory-hydraulika.gif... [Read more]
There are few good illustrations of such phenomena, but you can find something: Resistance and power The rule of the right hand The rule of the left hand [Read more]
Well on the course for an electrical qualification certificate (colloquially, SEP), the instructor, in this picture, explained to some people what voltage, current or resistance. [Read more]
In total, I have the impression that this picture of the Internet more than visited the world :D [Read more]
There are also several newer versions: https://engineersforfuture.wordpress.com/2017/01/30/ohms-law/ http://www.murcal.com/resources/resources_advice_ohms_law.html https://www.ecigarettedirect.co.uk/ashtray-blog/wp-content/uploads/2014/09/join-the-resistance.jpg... [Read more]
There were many drawings in "Electronics easier than you think". I have put a few scans here: https://www.elektroda.pl/rtvforum/viewtopic.php?p=15644172#15644172 It is worth coming back to this,... [Read more]
Perhaps I borrowed my avatar from a book, I do not remember. I've been through too much. They systematically explained the issues to the soldiers, unfortunately courses in English. https://ww... [Read more]
In mass culture, and this cretinism is repeated people who are considered to be electronics / electricians Ohm's law is the version of "current is spreading on the line of the least resistance", or... [Read more]
It is unfortunate that there is overinterpretation and, as a result, even various heresies. Half poor when a middle school / high school student will say yes, but not a professional electronics. ... [Read more]
Exactly, I was faced with the idea that current would flow ONLY through the smaller of the two parallel resistors :cry: greetings [Read more]
Sometimes, in the very middle of technical sciences, I will VERY associate with the humanities. Indeed, their rhetoric was too much of a sackcloth (Marek Tulliusz was in the grave) tautology... [Read more]
Smaller - size or resistance? How size is: Someone might have been right - in Wcz systems, as well as inverters where there are pins with a short time, with resistors with the same resistance, but... [Read more]
And right, but then it was a different situation :) [Read more]
Statements of such my "students": 1. This diagram consists of a resistor with voltage and a second resistor. Two-stage voltage setting because the resistor (1) causes the voltage to decrease in this... [Read more]
https://obrazki.elektroda.pl/2791846500_1559214457_thumb.jpg In my school there was such a picture in the electrotechnical workshop. [Read more]
Here is a very similar picture in the Polish version: Ohm's Law for fun [Read more]
This picture of Gulson appeals to me the most. Poor ampere ... And by the way, laymen do not distinguish it. Because they don't have to do it (and it comes out later when they look for advice on the... [Read more]
As I am glad that with my speech 5 years ago I was praised in the New Year. It was just a simple matter that the kettle, fridge, ... is only resistance for an electrician. Resistance to the flowing current... [Read more]