Does the positive charge of a proton add to its mass?
Nope. A positive charge is a characteristic not made up of matter (much like light or sound), and therefore doesn’t add to mass. In fact, having a positive charge makes it so that the proton is lighter than the neutral neutron. Interesting but potentially confusing explanation: This is because the proton is basically a neutron without an electron. Neutrons and protons are both made up things called quarks. Neutrons and protons have the same quark make-up except the neutron has a “down” quark instead of an “up” quark in the proton. The “down” quark is made up of an “up” quark and an electron. That’s why electrons are so light and small compared to neutrons and quarks; they help make up neutrons and protons.
