Energy Transformations

A lamp that plugs into a wall socket draws energy, which flows through a thin wire in the bulb, causing it to heat up until it glows. What energy transformations are taking place?

• Chemical → light → electrical

• Mechanical → sound → light

• Thermal → solar → electrical

• Electrical → thermal → light

An electric pencil sharpener uses electricity to make its motor spin. The pencil sharpener also makes noise and heats up. Which observation of the pencil sharpener demonstrates the law of conservation of energy?

• The amount of electrical energy used equals the total amount of mechanical, sound, and thermal energy produced.

• The amount of energy used by the electric pencil sharpener is greater than an electric lamp.

• The electric pencil sharpener only uses energy when it is being used to sharpen a pencil.

• The electric pencil sharpener is easier to use than the older version that was cranked by hand.

Tags

NGSS.MS-PS3-5

Turning the handle makes a current that causes the light bulb to glow. What are the energy transformations that happen in this hand generator?

• Thermal → solar → light

• Mechanical → electrical → light

• Electrical → mechanical → light

• Solar → light → electrical

When energy enters a system and then comes out of the system later, the law of conservation of energy states that–

• some of the energy that entered the system will remain in the system.

• the energy will always create a change in the properties of the parts of the system.

• the form of energy that comes out of the system must be the same form that entered.

• the amount of energy coming out of the system must equal the energy that entered the system.

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-5

In which of the following scenarios would this energy transformation be observed?

chemical → light → heat

• Plucking a guitar string

• Lighting a match

• Turning on a fan

• Starting a car

Tags

NGSS.MS-PS3-5

Which of the following is a form of potential energy?

• sound energy

• chemical energy

• mechanical energy

• thermal (heat) energy

Tags

NGSS.MS-PS3-2

The law of conservation of energy states ___.

• electrical energy can be transformed into other forms

• energy can be created and destroyed

• energy is never created nor destroyed

• what goes up must come down

During energy transformations, energy is never ___.

• released as heat

• used to increase an object's potential energy

• created or destroyed

• completely transformed

Tags

NGSS.MS-PS3-5

___ is energy stored by things that stretch or compress.

• Gravitational potential

• Elastic kinetic energy

• Chemical kinetic energy

• Elastic potential energy

Calculate the gravitational potential energy of the object.

GPE = mgh

mass: 50

gravity: 10

height: 6

• 5320J

• 300J

• 66J

• 3000J

Tags

NGSS.MS-PS3-2