A Level Physics Practice Exam

Which force acts between an up quark and an electron and involves an exchange particle?

1. Weak force

2. Strong force

3. Electromagnetic force

4. Gravitational force

The correct answer is: Weak force

The interaction between an up quark and an electron is primarily governed by the weak force, which is responsible for processes that involve the changing of particle types, such as beta decay. The weak force operates at a very short range and is mediated by the exchange of W and Z bosons, which are the force-carrying particles for this interaction. In this case, when we consider processes involving quarks (which are bound within protons and neutrons) and electrons, their interaction can occur through the exchange of virtual W bosons. This is a characteristic of the weak force, as it allows for flavor changes in quarks (for instance, an up quark can change into a down quark) and interacts with particles such as electrons. Understanding the context of other forces helps clarify why the weak force is the appropriate choice here: the strong force binds quarks together within protons and neutrons, but does not directly involve the interaction with electrons. The electromagnetic force does interact with charged particles like quarks and electrons, but a direct exchange involving a quark and an electron typically requires the weak force due to the changing nature of the particles involved. Gravitational force, although universal, is negligibly weak at the particle scale and