Coulomb's law and Electric Field

Multiple Select

Balloons 1 and 2 are tied to strings attached to a table and are attracted to each other, as shown in the figure. Balloon 1 has no net charge. Which of the following statements about the balloons are correct? Select two answers.

• Balloon 2 must be positively charged because 

        it must be attracting electrons in the atoms of

        balloon 1.

• Balloon 2 can have either a net positive charge

      or a net negative charge.

• Balloon 2 exerts an electric force on balloon 1

       because it induces charge separation in

       balloon

• Balloon 2 does not exert an electric force on   

      balloon 1 because balloon one has zero net

      charge.

Multiple Choice

Fred the lightning bug has a mass m and a charge +q. Jane,

his lightning-bug wife, has a mass $$\frac{3}{4}m$$ of and a charge -2q

Because they have charges of opposite sign, they are

attracted to each other. Which is attracted more to the

other, and by how much?

• Fred, twice as much.

• Jane, twice as much.

• Fred, four times as much.

• Jane, four times as much.

• They are attracted to each other by the same

  amount.

Open Ended

What are the differences and similarities between coulomb’s force and gravitational force?

Open Ended

where could you place a fourth charge(approximately), $$Q_4=-50\ \mu C$$ , so that the net force on $$Q_3$$

would be zero? Justify your answer.

Multiple Choice

A negative point charge is in an electric field created by

a positive point charge. Which of the following is true?

• The field points toward the positive charge, and the

  force on the negative charge is in the same direction as

  the field.

• The field points toward the positive charge, and the

  force on the negative charge is in the opposite direction

  to the field.

• The field points away from the positive charge, and the

  force on the negative charge is in the same direction as

  the field.

• The field points away from the positive charge, and the

  force on the negative charge is in the opposite

  direction to the field.

Multiple Choice

An electric dipole consists of two small spheres which carry charges of equal magnitude q and opposite signs as shown in the figure. The center of the dipole is at the origin. Two labeled points M and N are on the y–axis and x-axis, respectively. An electron is released from rest at point M. Which of the following vectors indicates the direction of the electron’s initial acceleration?

• The direction will be undefined, because the electron will remain at rest.

• ←

• →

• ↑

• ↓

Multiple Choice

*The figure above shows an object in the shape of an arc. The object has a uniform charge distribution. The three labeled vectors show possible directions of the electric field at point P at the center of the arc. Which of the following options indicates the vector that shows the correct direction of the electric field and provides a correct physical explanation for this direction?

• Vector A; the charge distribution is positive, and there are more charges to the left of point P.

• Vector B; the charge distribution is negative, and there are more charges to the left of point P.

• Vector C; the charge distribution is positive, and there are more charges above point P.

• Vector B; the charge distribution is negative, and there are more charges above point P.

• Vector C; the charge distribution is positive, and there are no charges below and to the left of point to cancel the field from charges above and to the right of point P.