3106: Farads

2025-06-25T12:21:54Z

2001:4C4E:1C11:8E00:18AE:4016:7CEB:270D: /* Explanation */

{{comic
| number = 3106
| date = June 23, 2025
| title = Farads
| image = farads_2x.png
| imagesize = 677x253px
| noexpand = true
| titletext = 'This HAZMAT container contains radioactive material with activity of one becquerel.' 'So, like, a single banana slice?'
}}

==Explanation==
This comic shows Cueball showing off several items that (he claims) comprise approximately one of a given unit, with Megan and White Hat reacting appropriately.

The first three — meters, pounds and volts — are all units of which “1” is a not extraordinary amount for an item that can be easily held in the hand.

However, 1 {{w|farad}} is an unusual amount of capacitance. In common use, most consumer electronics use capacitors in the picofarad to millifarad range, and 1 millifarad is already considered a "large" capacitor. A 1-farad capacitor is considered a supercapacitor. Cueball claiming to have a 1-farad capacitor elicits unwarranted panic from Megan and White Hat, who fear that it could be very dangerous, and ask why he's carrying it around. In reality, any hand-held 1 farad capacitor will have a very low voltage limit and therefore not be in any way dangerous.

Capacitance (C) is the ratio between charge (coulombs or amp-seconds) and electromotive force (V, volts or joules per coulomb).

The title text explores the inverse situation, where “1” of a unit is a very small amount. A becquerel amounts to one radioactive decay per second on the atomic level, which is a really low level of radioactivity. As observed, the material in question could be a single slice of a banana (primarily due to the decay of trace potassium-40 in the total potassium it contains). Hence, it is both impractical and unnecessary to contain it inside a container for hazardous materials unless the material is dangerous for other reasons (such as corrosiveness or flammability). In comparison, the human body itself [https://web.archive.org/web/20200220103556/https://radioactivity.eu.com/site/pages/Activity_Doses.htm has an activity of 8000 Bq].

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
: [Cueball holds a stick while talking with Megan and White Hat.]
: Cueball: This stick is one meter long.
: Megan: Cool.
: White Hat: That's a nice stick.

: [Cueball holds a smallish rock.]
: Cueball: This rock weighs one pound.
: Megan: I'd believe it.
: White Hat: Looks like a normal rock.

: [Cueball holds a small battery.]
: Cueball: This battery is one volt.
: Megan: Seems fine.
: White Hat: Might need a recharge.

: [Cueball holds a capacitor while Megan and White Hat panic.]
: Cueball: This capacitor is one farad.
: Megan: Aaaaa! Be careful!!
: White Hat: Put it down!!

{{comic discussion}}<noinclude>
[[Category: Comics featuring Cueball]]
[[Category: Comics featuring White Hat]]
[[Category: Comics featuring Megan]]
[[Category: Physics]]

explain xkcd - User contributions [en]

3106: Farads