iPhone Screenshots


Ohm's law and the power law describe the relationship between the following four electrical entities:


Current..........Amps.....A, I
Resistance...Ohms.....Ω, R

Ohm's law: Voltage = Current x Resistance
Power law: Power = Voltage x Current

Set any two, and the other two can be calculated.

This application allows you to continually lock one parameter and input another, enabling rapid "what-if" recalculation.

Use the keypad to enter a value then tap on the parameter you want to set. It is now fixed, as shown by the padlock symbol.

Enter another parameter and the remaining two are calculated. The most recently entered parameter becomes the new fixed one.

You can alter which parameter is fixed by tapping it when the input box is empty, or by dragging the padlock to it.

You can 'Freeze' a parameter with a long press until it changes colour. Now alter any of the other three as required. To unfreeze, with the input box empty, tap any other parameter.

The value of the fixed parameter may not be changed. If you attempt to do so, the padlock will flash. In this case, fix another parameter first.

Available in the following Languages:
English, French, German, Swedish, Russian, Polish, Spanish, Italian, Chinese (Traditional & Simplified).

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If you find any errors, or have any suggestions, please email us the details & we will address them!


What’s New

Version 1.7

Latest iOS support(64 Bit). Minor UI improvements.

Ratings and Reviews

Mdarkness1988 ,

Needs updating for 64bit

From ios 11 releasing this year they are fully dropping 32bit apps and this app will then be invisible on the store.
Otherwise great app

Steve 990 ,

Quite a good app

This app appears to work OK. The issue of the disappearing values mentioned by some of the other reviews is valid, but movement of the padlock to the left of the values then keeps the entry on display. There are instruction now on the app also.

Naz564667 ,

Does not work

Wipes out figures after writing in voltage


Cressall Resistors Ltd
1.6 MB
Requires iOS 8.0 or later. Compatible with iPhone, iPad and iPod touch.
English, French, German, Hindi, Italian, Polish, Russian, Simplified Chinese, Spanish, Swedish, Traditional Chinese
Age Rating
Rated 4+
© 2017 Cressall Resistors Ltd


  • Family Sharing

    Up to six family members will be able to use this app with Family Sharing enabled.

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