Lesson 5.17 - Review Electric and Magnetic Forces

Two students hold two objects in place on a flat table. When the students let go of the objects, one object is pulled toward the other object. 

What are the two objects most likely to be?

• a length of wire and a D-cell battery

• a wood building block and an electromagnet

• a bar magnet and an electromagnet

• two toy trains

Answer explanation

The correct choice is a bar magnet and an electromagnet because when the students let go, the magnetic force between the two objects causes them to be pulled towards each other.

Tags

NGSS.MS-PS2-3

NGSS.MS-PS2-5

Static electricity may form when a material is _____​

• rubbed

• electrons

• opposite

Answer explanation

Static electricity may form when a material is rubbed, causing the transfer of electrons and creating an opposite charge imbalance.

Tags

NGSS.MS-PS2-3

NGSS.MS-PS2-5

Two balloons are each rubbed with a silk cloth and then placed on a wall. One balloon sticks to the wall, while the other balloon drops to the floor.

What are the two most likely reasons for the different outcomes?

Select the TWO correct answers.

• Different parts of the balloons were rubbed.

• The temperature of the room is unusually warm.

• The balloons are made of different materials.

• One balloon was rubbed more vigorously or longer than the other balloon.

• The balloon that sticks to the wall is heavier than the balloon that fell.

Answer explanation

The correct answers are that the balloons are made of different materials and one balloon was rubbed more vigorously or longer than the other balloon.

Tags

NGSS.MS-PS2-3

NGSS.MS-PS2-5

Two tiny metal shavings are 1 centimeter apart. Each shaving has an electric charge of 3 units.

How would changes to the shavings affect the electric force between them?

For each change, select Force Weakens or Force Strengthens.

The charge on one shaving is removed.

• Force Weakens

• Force Strengthens

Answer explanation

Removing the charge weakens the force between the shavings as the electric force is directly proportional to the product of the charges.

Tags

NGSS.MS-PS2-3

Two tiny metal shavings are 1 centimeter apart. Each shaving has an electric charge of 3 units.

How would changes to the shavings affect the electric force between them?

For each change, select Force Weakens or Force Strengthens.

The charge on one shaving is increased to 5 units.

• Force Weakens

• Force Strengthens

Answer explanation

Increasing the charge on one shaving to 5 units will strengthen the electric force between them due to the direct relationship between charge and electric force.

Tags

NGSS.MS-PS2-3

Two tiny metal shavings are 1 centimeter apart. Each shaving has an electric charge of 3 units.

How would changes to the shavings affect the electric force between them?

For each change, select Force Weakens or Force Strengthens.

The charge on each shaving is increased to 5 units.

• Force Weakens

• Force Strengthens

Answer explanation

Increasing the charge on each shaving will result in a stronger electric force between them, as the force is directly proportional to the product of the charges.

Tags

NGSS.MS-PS2-3

Two tiny metal shavings are 1 centimeter apart. Each shaving has an electric charge of 3 units.

How would changes to the shavings affect the electric force between them?

For each change, select Force Weakens or Force Strengthens.

The distance between the shavings is increased to 2 centimeters.

• Force Weakens

• Force Strengthens

Answer explanation

Force Weakens because as the distance between the shavings increases, the electric force between them decreases according to the inverse square law.

Tags

NGSS.MS-PS2-3

Two tiny metal shavings are 1 centimeter apart. Each shaving has an electric charge of 3 units.

How would changes to the shavings affect the electric force between them?

For each change, select Force Weakens or Force Strengthens.

The distance between the shavings decreased to one half a centimeter.

• Force Weakens

• Force Strengthens

Answer explanation

When the distance between the shavings decreases, the electric force between them strengthens due to the inverse square law of electric force.

Tags

NGSS.MS-PS2-3

Two small spoons are placed at the same distance from the poles of a bar magnet. One spoon is attracted to the magnet, while the other spoon experiences no magnetic force.

What property must differ between the two spoons?

• 
  

• • size

• texture

• type of material

• mass

Answer explanation

The property that must differ between the two spoons is the type of material, as different materials interact differently with magnetic fields.

Tags

NGSS.MS-PS2-3

A drone uses a magnetic compass to find its way. The drone flies near a powerful electromagnet, such as a magnet that lifts scrap metal at a junkyard.

How would the drone most likely be affected?

• The drone would fly faster and more accurately.

• The drone would stop flying and drop to the ground.

• The drone would fly in the wrong direction, and soon crash.

• The drone would be pushed away from the electromagnet.

Answer explanation

The drone would fly in the wrong direction, and soon crash due to interference with the powerful electromagnet.

Tags

NGSS.MS-PS2-3

NGSS.MS-PS2-5