Which of the following is NOT one of the three methods of charging?

The correct answer is radiation. The three primary methods of charging objects are conduction, induction, and friction.

Conduction involves direct contact between materials, allowing electrons to transfer from one object to another. This results in both objects acquiring the same charge or one becoming positively charged while the other becomes negatively charged based on the number of electrons transferred.

Induction, on the other hand, involves the rearrangement of electrical charges in an object without direct contact. When a charged object is brought close to a neutral object, it causes the charges within that neutral object to rearrange, leading to temporary polarization. When the charged object is removed, the induced object may retain a net charge if it is grounded.

Friction refers to the transfer of electrons when two different materials are rubbed together, often leading to one object losing electrons and becoming positively charged while the other gains electrons and becomes negatively charged.

Radiation does not pertain to the charging of objects in the same way; it involves the emission of energy as electromagnetic waves or particles and is not a method used to induce charge through direct contact, polarization, or transferring electrons. Thus, it does not belong to the recognized methods of charging.