A student rubs a rubber rod with fur, producing a negative charge on the rod. The student then touches the rod to a hollow, neutral metal sphere that stands on an insulating plastic stand. This transfers negative charges from the rod to the sphere:
Which statement best predicts what will happen to the charge, and why?
A. It will quickly spread to the air around the sphere, because it will seek to occupy as large a volume of neutral matter as possible.
B. It will remain at the point of contact between the rod and the sphere, because resistance in the metal prevents the charges from easily moving.
C. It will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.
D. It will slowly drift to the bottom of the sphere, because the charges rapidly attach to individual atoms, making them slightly heavier than surrounding atoms.
C. It will distribute itself evenly over the surface of the sphere, because like charges repel and the sphere is a conductor.
When the negatively charged rod is touched to the neutral metal sphere, the negative charges will repel each other and spread out as much as possible on the surface of the sphere. In a conductor, like charges are free to move, so they will distribute themselves evenly over the surface. This is known as electrostatic induction.
A student is investigating the distribution of charges in insulators. The student will place an aluminum metal can on top of a foam cup and touch the side of the foam cup with a negatively charged rod. The set up for the investigation is shown in the diagram.
What will MOST LIKELY happen to the electrons when the rod touches the foam cup?
A. The electrons will pass to the foam cup but will remain in a localized, positively charged area on the cup where the rod was placed.
B. The electrons will pass to the foam cup but will remain in a localized, negatively charged area on the cup where the rod was placed.
C. The electrons will pass from the foam cup to the aluminum can, and both the foam cup and the aluminum can will become positively charged.
D. The electrons will pass from the foam cup to the aluminum can, and both the foam cup and the aluminum can will become negatively charged.
A. The electrons will pass to the foam cup but will remain in a localized, positively charged area on the cup where the rod was placed.
When the negatively charged rod touches the foam cup, electrons will be transferred from the rod to the cup. However, since foam is an insulator, the electrons will not be able to move freely throughout the material. Instead, they will remain in a localized area, creating a positive charge where the rod was placed. The rest of the cup will still be neutral.
A student is designing an investigation of the distribution of charges in conductors. She will use two conducting spheres mounted on insulating stands in the investigation. The conducting spheres are shown.The student wants to separate the charges of the spheres as shown.What should the student do in her investigation to produce these results?
A. She should place a negatively charged rod near the left sphere.
B. She should place a positively charged rod near the left sphere.
C. She should place two negatively charged rods near each sphere.
D. She should place two positively charged rods near each sphere.
D. She should place two positively charged rods near each sphere.
To separate the charges of the spheres as shown, the student needs to add a positive charge to the left sphere and a negative charge to the right sphere. By placing two positively charged rods near each sphere, the positive charges will be transferred to the spheres, resulting in a positive charge on the left sphere and a negative charge on the right sphere.