Electricity Review

How is Coulomb's law similar to the Universal Gravitational Law?

• They both use the mass of an object to determine the force between objects.

• They both share the same constant used in calculations.

• They both use the charge of an object to determine the force between objects.

• They are both inverse square laws.

Answer explanation

Coulomb's law and the Universal Gravitational Law are both inverse square laws, meaning the force between two objects decreases with the square of the distance between them. This similarity highlights their mathematical structure.

Tags

NGSS.HS-PS2-4

• 5.6 x 10^1 N

Answer explanation

Using Coulomb's law, F = k * |q1 * q2| / r². Here, k = 8.99 x 10^9 N m²/C², q1 = 6.00 x 10^-6 C, q2 = -6.00 x 10^-6 C, and r = 0.06 m. Calculating gives F = 8.99 x 10^1 N, which matches the correct answer.

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NGSS.HS-PS2-4

NGSS.HS-PS3-5

Using Coulomb's law, the distance between the center of charges, and scientific notation, calculate the magnitude of the net electric force on charge q1 when q1=10 μC and q2=−5 μC, with a distance of 3.00 cm.

• 8.99 x 10^9 N

• 4.99 x 10^2 N

Answer explanation

Using Coulomb's law, F = k * |q1 * q2| / r^2, where k = 8.99 x 10^9 N m^2/C^2, q1 = 10 x 10^-6 C, q2 = -5 x 10^-6 C, and r = 0.03 m. Calculating gives F = 4.99 x 10^2 N, confirming the correct choice.

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NGSS.HS-PS2-4

• 3.86 m

• 1.96 m

• 5.00 m

• 2.99 m

Answer explanation

Using Coulomb's law, F = k * |q1 * q2| / r^2, we can rearrange to find r. Plugging in the values (F = 0.07 N, q1 = 6.00e-6 C, q2 = -5.0e-6 C), we calculate r to be approximately 3.86 m, confirming the correct choice.

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NGSS.HS-PS2-4

Oliver, Aria, and Henry are comparing the strength of point charges they have. Rank the point charges from weakest to strongest based on the field lines shown in the image.

• A, B, C

• C, B, A

• B, A, C

• C, A, B

Answer explanation

The strength of point charges is indicated by the density of the field lines. In the image, charge C has the least dense lines, followed by B, and A has the most dense lines, making the correct ranking from weakest to strongest: C, B, A.

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NGSS.HS-PS2-4

NGSS.HS-PS3-5

Choose the correct statement describing the image shown below of two point charges.

• Charge A is negative and Charge B is positive and the charges will repel

• Charge A is negative and Charge B is positive and the charges will attract

• Charge A is positive and Charge B is negative and the charges will repel

• Charge A is positive and Charge B is negative and the charges will attract

Answer explanation

Charge A is negative and Charge B is positive. Opposite charges attract each other, so the correct statement is that the charges will attract.

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NGSS.HS-PS3-5

Samuel is observing a storm and notices that the lightning strikes are getting closer together. What does this indicate about the electric field in the area?

• The electric field is inversely proportional to the density of electric field lines.

• The electric field is directly proportional to the density of electric field lines.

• The electric field is not related to the density of electric field lines.

• The electric field is inversely proportional to the square root of density of electric field lines.

Answer explanation

When electric field lines are closer together, it indicates a stronger electric field. Therefore, the electric field is directly proportional to the density of electric field lines, making the correct choice the second option.

Scarlett and Michael are conducting an experiment with two unlike charges of equal magnitude. What is the shape of the electric field lines between these charges?

• Curved lines bending toward one another

• Circular lines criss crossing each other

• Curved lines bending away from each other

• Random lines shooting out at various angles

Answer explanation

The electric field lines between two unlike charges (one positive and one negative) curve toward each other, indicating attraction. This is why the correct answer is 'Curved lines bending toward one another'.

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NGSS.HS-PS3-5

Which process best describes triboelectric charging?

• Transfer of charge through a conducting wire

• Transfer of charge when two materials are rubbed together and then separated

• Transfer of charge without direct contact

• Redistribution of charge due to an external electric field

Answer explanation

Triboelectric charging occurs when two different materials are rubbed together, causing electrons to transfer from one material to the other. This process results in one material becoming positively charged and the other negatively charged upon separation.

Two small spheres, one with a charge of +4 units and the other with a charge of -4 units, are brought into contact and then separated. What are the charges on each sphere after separation?

• +4 units on each sphere

• -4 units on each sphere

• +2 units on each sphere

• 0 units on each sphere

Answer explanation

When the two spheres are brought into contact, they share their charges equally. The total charge is +4 + (-4) = 0 units. After separation, each sphere has 0 units of charge.

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NGSS.HS-PS3-5