Variable electromagnet help

[Norm!]

Hello. I am new to both electronics and this forum.
I have an idea for what I hope is a fairly simple first project, I want to build a small, battery powered electromagnet with the ability to vary the strength of the magnet during use.
In my layman's world some kind of variable potentiometer is what I'm thinking.
I've tried Internet searches with no success so far.
Any and all thoughts gratefully received.
Thank you.

 

[Minder]

Simple PWM based on such as this, http://www.discovercircuits.com/DJ-Circuits/simplepwm2.htm
M.

 

[Alec_t]

Welcome to EP.
What will you use the electromagnet for? A strong electromagnet will quickly drain a small battery.