A teacher places a metal can on top of an insulating foam cup and touches the side of the cup with a negatively charged rod. The setup is shown in the picture below.
What will happen to the negatively charged electrons when the rod touches the foam cup?
A The electrons will transfer from the cup to the metal can, causing both cup and can to have a positive charge.
B The electrons will transfer to the cup and will remain in a concentrated, negatively charged area on the cup where the rod was placed.
C The electrons will transfer from the cup to the metal can, causing both the cup and can to have a negative charge.
D The electrons will transfer to the cup and will remain in a concentrated, positively charged area on the cup where the rod was placed.
C The electrons will transfer from the cup to the metal can, causing both the cup and can to have a negative charge.
A The electrons will transfer from the cup to the metal can, causing both cup and can to have a positive charge.
To determine what will happen to the negatively charged electrons when the rod touches the foam cup in this setup, we need to understand the concept of conduction.
Conduction is the process in which charge is transferred between objects that are in direct contact. When a negatively charged rod touches the foam cup, the electrons from the rod will transfer to the cup via conduction.
Now let's consider the options:
A. The electrons will transfer from the cup to the metal can, causing both the cup and can to have a positive charge.
This option is incorrect because the electrons will actually transfer from the rod to the cup, not from the cup to the can.
B. The electrons will transfer to the cup and will remain in a concentrated, negatively charged area on the cup where the rod was placed.
This option is incorrect because the electrons will disperse throughout the cup, not remain concentrated in one area.
C. The electrons will transfer from the cup to the metal can, causing both the cup and can to have a negative charge.
This option is incorrect because the electrons will transfer from the rod to the cup, not from the cup to the can.
D. The electrons will transfer to the cup and will remain in a concentrated, positively charged area on the cup where the rod was placed.
This option is correct. When the rod touches the foam cup, the negatively charged electrons from the rod will transfer to the cup. The cup will then become negatively charged in the area where the rod made contact, while the rest of the cup remains neutral. The electrons will not transfer to the metal can, as it is not in direct contact with the rod.
Therefore, the correct answer is option D: The electrons will transfer to the cup and will remain in a concentrated, positively charged area on the cup where the rod was placed.