Unit 3 Test: Electricity & Magnetism

Select all the correct answers. According to Newton’s law of universal gravitation, which statements are true?

• As we move to higher altitudes, the force of gravity on us decreases.

• As we move to higher altitudes, the force of gravity on us increases.

• As we gain mass, the force of gravity on us decreases.

• As we gain mass, the force of gravity on us increases.

• As we move faster, the force of gravity on us increases.

Answer explanation

As we move to higher altitudes, gravity decreases due to the increased distance from the Earth's center. Conversely, as we gain mass, the gravitational force we exert increases, aligning with Newton's law.

Select all the correct answers. An unmanned spacecraft leaves for Venus. Which statements about the spacecraft’s journey are true?

• The weight of the spacecraft keeps changing.

• The mass of the spacecraft keeps changing.

• The weight of the spacecraft remains the same.

• The mass of the spacecraft remains the same.

• The gravitational pull on the spacecraft remains the same.

Answer explanation

The weight of the spacecraft changes due to varying gravitational forces as it travels, while its mass remains constant since it does not lose or gain material.

Select all the correct answers. Antonio is holding a 1-pound bag of apples in his left hand and a 2-pound bag of apples in his right hand. Which sentences about this situation are true?

• The force caused by gravity is the same on each bag.

• Antonio is applying a 1-pound force to hold the 1-pound bag.

• Antonio must apply a greater force to hold the 1-pound bag than the 2-pound bag.

• The acceleration due to gravity is greater on the 2-pound bag.

• The mass of the bag in his left hand is less than the mass of the bag in his right hand.

Answer explanation

Antonio applies a 1-pound force to hold the 1-pound bag, as force equals weight. The mass of the bag in his left hand (1 pound) is less than that in his right hand (2 pounds), making these statements true.

Select the correct location on the image. The image shows the positions of the Earth and the Moon. In which region would an astronaut feel the lightest?

When people use plastic combs on their hair, the combs become negatively charged. Which statements about this situation are true?

• The comb loses electrons.

• The comb gains electrons.

• The hair loses electrons.

• The hair gains protons.

• The hair loses protons.

Answer explanation

When a plastic comb is used on hair, it gains electrons, becoming negatively charged. Consequently, the hair loses electrons, resulting in a positive charge. Thus, the correct statements are that the comb gains electrons and the hair loses electrons.

Categorize using the correct force for each column.

Groups:

(a) What force and magnitude btwn B&CB & C

,

(b) What force and magnitude btwn A&D

• Attraction

• Force of attraction

• Maximum

• Minimum

Which item is magnetic?

​ ​ (a)   ​ ​ (b)   ​ ​ (c)  

​ ​ ​

• Steel Tank

• Iron Ball

• Nickel Hinge

• Wooden Table

• Glass marbles

Answer explanation

The Steel Tank, Iron Ball, and Nickel Hinge are all made of ferromagnetic materials, which can be magnetized. In contrast, the Wooden Table and Glass marbles are non-magnetic.

Which item is nonmagnetic?

​ ​ ​ ​ ​ ​ ​ (a)  

​ (b)   ​ (c)  

• Iron Ball

• Glass Marble

• Steel Tank

• Wooden Table

• Silver Medal

• Nickel

Answer explanation

The Glass Marble, Wooden Table, and Silver Medal are nonmagnetic materials. In contrast, Iron, Steel, and Nickel are magnetic, making them unsuitable choices.

Click on the charge that will allow object A to become positively charged.

What is the resistance of a circuit with a voltage of 10 volts (V) and a current of 5 amps (A)? Use Ohm’s law to calculate the resistance.

• 2 ohms

• 5 ohms

• 10 ohms

• 0.5 ohms

Answer explanation

Using Ohm's law, R = V/I. Here, V = 10 volts and I = 5 amps. Thus, R = 10V / 5A = 2 ohms. Therefore, the correct answer is 2 ohms.