Q: If three positive charges are aligned as shown: $$+0.10\,C (A$$), $$+0.02\,C (B$$), $$+0.04\,C (C$$), with distances $$AB = 2\,m$$ and $$BC = 1\,m$$, what is the net force on charge B due to A and C? ($$k = 8.99 \times 10^9$\,N \cdot m^2$/C^2$)

$$2.7 \times 10^6$\,N to $$the left

Question 1

Which of the following is NOT one of the four fundamental forces in the universe?

Accepted Answer

Friction

Question 2

Which statement best describes the difference between a vector and a scalar quantity?

Accepted Answer

A scalar has magnitude only, while a vector has both magnitude and direction.

Question 3

Which of the following is a scalar quantity?

Accepted Answer

Temperature

Question 4

Coulomb’s Law describes the force between two point charges. Which equation correctly represents this law?

Accepted Answer

$$F = k \frac{q_1$ q_2$}{r^2$}$$

Question 5

Two charges, $$q_1 = 2$$ \mu C$$ and q_2$ = 7 \mu C$$, are separated by $$r = 0.2\,m. $$What is the magnitude of the electrostatic force between them? ($$k = 8.99 	imes 10^9$\,N \cdot m^2$/C^2$)

Accepted Answer

$$3.15\,N$$

Question 6

Which of the following best explains why electricity is much stronger than gravity at the atomic scale?

Accepted Answer

The Coulomb force is proportional to charge, which is much larger in effect than mass at small scales.

Question 7

A force of $$2.3 	imes 10$$^{-8}$$\,N$$ acts on an electron in a hydrogen atom due to the proton. If $$r = 1 	imes 10$$^{-10}$$\,m$$, what is the value of the charges used in the calculation?

Accepted Answer

$$1.6 	imes 10$$^{-19}$$\,C$$

Question 8

Which of the following is true about electric charge?

Accepted Answer

The net charge of a closed system never changes.

Question 9

If three positive charges are aligned as shown: $$+0.10\,C (A$$), $$+0.02\,C (B$$), $$+0.04\,C (C$$), with distances $$AB = 2\,m$$ and $$BC = 1\,m$$, what is the net force on charge B due to A and C? ($$k = 8.99 	imes 10^9$\,N \cdot m^2$/C^2$)

Accepted Answer

$$2.7 	imes 10^6$\,N to $$the left

Question 10

Which of the following is a correct application of the principle of superposition for forces?

Accepted Answer

The total force is the vector sum of all forces acting on a charge.

Question 11

A student adds two vectors using the tail-to-head method. Which statement is correct?

Accepted Answer

The resultant vector is drawn from the tail of the first vector to the head of the last vector.

Question 12

Which of the following is a correct strategy for solving force problems involving multiple charges?

Accepted Answer

Draw a clear force diagram and use consistent units.

Question 13

In a triangle arrangement, a $$+2.0\,\mu C$$ charge is at the top, $$+7.0\,\mu C at $$the bottom left, and $$-3.5\,\mu C at $$the bottom right. What is the first step to find the net force on the $$+2.0\,\mu C$$ charge?

Accepted Answer

Calculate the force from the $$+7.0\,\mu C$$ charge.

Question 14

Which of the following best describes the direction of the force between two like charges?

Accepted Answer

Repulsive and along the line joining the charges.

Question 15

A positive and a negative charge of equal magnitude are connected by a rigid rod and placed near a large negative charge. What is the direction of the net force on the rod?

Accepted Answer

Away from the large negative charge

Question 16

Which of the following is true about conductors and insulators?

Accepted Answer

Conductors allow electric charge to move freely, while insulators do not.

Question 17

If the distance between two point charges is doubled, what happens to the electrostatic force between them?

Accepted Answer

It becomes one-fourth as large.

Question 18

Which of the following is the correct value for the electric constant (permittivity of free space) $$\$$varepsilon_0$$?

Accepted Answer

$$8.85 	imes 10$$^{-12}$$\,C^2$/(N \cdot m^2$)$$

Electric Charge, Coulomb's Law, and Vector Quantities: Study Notes for College Physics

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