/diy/ - Do It Yourself

I decided to try and find a method to measure the current flowing through an AC cable, I used a 60W light bulb as a load (0.3 amps) and I placed several toroids along the wire and measured the voltage with the scope just to find there isn't any noticeable change in the voltage. What am I doing wrong? Are the toroids? Or maybe I havent used enough turns?

The reason I'm doing this is because I want to install an electronic fuse to make a tesla coil, in case the current raises too much a relay should open avoiding further damage.
I was thinking about using an OP amp to do this. Is there a better way?