AP Physics 2: Electric Fields

What happens to the field strength as the distance between two charged objects decreases?

• the strength stays the same

• the strength increases

• the strength decreases

• the strength fluctuates between positive and negative

Answer explanation

The field strength between two charged objects is directly proportional to the product of their charges and inversely proportional to the square of the distance between them, according to Coulomb's Law. As the distance between the objects decreases, the field strength increases, making the correct choice 'the strength increases'.

Tags

NGSS.HS-PS2-4

A charged particle traveling along the +x axis enters an electric field directed vertically upward along the +y-axis. If the charged particle experiences a force downward because of this field, what is the sign of the charge on this particle?

• It is negative.

• It is positive.

• It is neutral.

• None of the other choices is correct.

Answer explanation

The charged particle experiences a force downward due to the electric field directed vertically upward along the +y-axis. This indicates that the particle has a negative charge, as it is attracted in the opposite direction of the electric field. Therefore, the sign of the charge on this particle is negative.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

Three equal point charges are placed at the corners of a square of side d as shown in Figure 19-9. Which of the arrows shown represents the direction of the net electric field at the center of the square?

• A

• B

• C

• D

Answer explanation

The net electric field at the center of the square is the vector sum of the electric fields due to each point charge. Since the charges are equal, their electric fields at the center have equal magnitudes. The electric field due to the diagonal charges cancels out, leaving only the electric field due to the bottom-left charge, which points towards the top-right corner.

Tags

NGSS.HS-PS3-5

Three equal point charges are placed at the corners of a square of side d as shown in Figure 19-9. What is the correct expression of the net electric field at the center of the square?

Answer explanation

The net electric field at the center of the square can be found by calculating the electric field due to each charge and summing them up. Since the charges are equal and placed symmetrically, their electric fields will add up constructively. The correct expression for the net electric field is E = (k2q) / (d^2), as it takes into account the contributions from all three charges.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

Three equal point charges of varying signs are placed on the corners of a square of side d as shown in Figure 19-10. Which of the arrows shown represents the direction of the net electric field at the center of the square?

• A

• B

• C

• D

Answer explanation

In the given question, three equal point charges are placed on the corners of a square. The net electric field at the center of the square will be the vector sum of the electric fields due to each charge. Since the charges have varying signs, the net electric field will be in the direction of the positive charge, which is represented by arrow A.

Tags

NGSS.HS-PS3-5

Three equal point charges are placed at three of the corners of a square of side d as shown in Figure 19-12. Which of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

• A

• B

• C

• D

Answer explanation

In the given question, three equal point charges are placed at three corners of a square. The net electric field at the vacant corner is the vector sum of the electric fields due to each charge. Since the charges are equal, the electric fields due to the charges on the diagonal will cancel each other out, leaving only the electric field due to the charge on the adjacent corner. This results in a net electric field pointing away from the adjacent charge, which is represented by arrow B.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

A proton is placed in an electric field of intensity 700 N/C. What is the magnitude and direction of the acceleration of this proton due to this field?

• 6.71 × 10^20 m/s2 opposite to the electric field

• 6.71 × 10^9 m/s2 opposite to the electric field

• 6.71 × 10^10 m/s2 in the direction of the electric field

• 67.1 × 10^10 m/s2 in the direction of the electric field

Answer explanation

The acceleration of a proton in an electric field can be calculated using the formula a = F/m, where F is the force on the proton and m is its mass. The force on the proton is given by F = qE, where q is the charge of the proton and E is the electric field intensity. By substituting the values, we get a = (1.6 × 10^-19 C × 700 N/C) / (1.67 × 10^-27 kg), which results in an acceleration of 6.71 × 10^10 m/s2 in the direction of the electric field.

Tags

NGSS.HS-PS2-1

A styrofoam ball of mass 0.120 g is placed in an electric field of 6000 N/C pointing downward. What charge must be placed on the ball for it to be suspended?

• -16.0 nC

• -18.0 nC

• -57.2 nC

• -125 nC

• -196 nC

Answer explanation

The question asks for the charge needed to suspend a styrofoam ball in an electric field. The force on the ball due to the electric field must equal the gravitational force on the ball. By using the formula F = qE = mg, we can solve for q (charge). The correct answer is -196 nC, which balances the forces and suspends the ball.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

Where can an electric field be found?

• below a force field

• in a gravitational field

• in the space surrounding a charged object

• outside of a magnetic field

Answer explanation

An electric field exists in the space surrounding a charged object. This field represents the force that a positive test charge would experience at any point in space due to the presence of the charged object. Therefore, the correct answer to the question is 'in the space surrounding a charged object'.

Electrical field lines of a negatively charged object flow _______________.

• Inwards

• Outwards

• Clockwise

• Counter-Clockwise

Answer explanation

The electrical field lines of a negatively charged object flow inwards. This is because electric field lines always originate from positive charges and terminate at negative charges. In the case of a negatively charged object, the field lines would be entering the object, hence, they flow inwards.