Unlike Earth, Venus doesn’t have a magnetic field,
is that because it’s a rock and doesn’t have a liquid core?
But despite the planets' similarities, the magnetic field of Venus is far weaker than on Earth's. The reasons for that may have to do with the core. Part of it could simply have to do with motion. The planet spins very slowly — once every 243 Earth days — and the core may not spin fast enough to create a magnetic field the way the core of Earth and other planets do. The core may also be completely solid, or may not even exist at all. Taking readings on the interior of another planet is a significant challenge.
Earth’s core has a lot more metal, some from the other planet that hit it, churning the core and making the moon from lighter material kicked off. Venus has less temperature gradient to fuel convection. And earth spins a lot faster. Moving magnets generate more current.