Respuesta :

through friction between her feet and the carpet 

Explanation :

Tracy scuffs her socked feet across a carpet. When she touches a doorknob, she gets a small shock. This is due to the concept of static electricity.

Charging by friction is one of the methods of charging. When two insulators are rubbed against each other, electrons get transferred from one material to another.

On rubbing her feet across a carpet, the negatively charged electrons get transferred from the carpet to her body. This continues until there is an equilibrium of electrons is reached between the carpet and the body.

Due to this, a potential is created and the body will act as a voltage source. Now when her hand comes in contact with the metal doorknob, the electrons move from her body to metal piece. So, she gets a small shock.