My course

If C(max) = E(max).B(max) does C(rms) = E(rms).B(rms)

I'm confused as to why we do mg times cosfeta for the friction force. I looked at the image in the older comments and cosfeta is in the y direction, however, I thought that the frictional force is in the horizontal direction so why don't we use sinfeta?

Hi there! The positive (longer plate) of the battery is shown - Current flows from long plate to short plate. If we make our fingers follow the current and curl, our thumb points out of the page.

Thumb direction practice: Try putting the fingers against the current and see if your thumb points into the page. You should realize that the thumbs direction is affected by direction of fingers.

Ensure fingers take direction of current to get the setup correct.