Electric Circuits & Energy Flow
What is the purpose of a switch in an electrical circuit?
To allow the circuit to be opened or closed easily.
Why can you see your reflection in a mirror?
Because light bounces (reflects) off the mirror back to your eyes.
If a shirt feels hotter than another in the sun, what can you infer about its color?
It’s a darker color that absorbs more light (and heat).
How does light help us see objects?
Light reflects off objects and enters our eyes.
What kind of energy transformation happens in a toaster?
Electrical → Thermal energy
Why does a mobile phone need a battery?
To provide energy for light and sound.
Why does a spoon look bent in a cup of water?
Because light bends (refracts) as it moves between air and water, cause the spoon to look bent in the cup of water.
What happens when an object absorbs nearly all the light that strikes it?
It appears black or very dark.
Which form of energy do our eyes detect?
Light energy
What energy change occurs in a lamp?
Electrical → Light energy
What happens when a circuit is open?
The electric current stops flowing.
When light bends as it passes from air into water, what property is demonstrated?
Refraction
Why does a basketball look orange in sunlight?
It reflects orange light and absorbs all other colors.
What type of surface does light best bounce off of? What are two additional examples to go along with a mirror?
Smooth and shiny surfaces.
Metal, Water
How does a radio transform energy?
Electrical → Sound energy
What is the path of electric current in a closed circuit?
Current flows from the energy source → through wires → to the device → back to the source.
Is the following situation an example of reflection or refraction? Why?
A rainbow forming after a rain shower.
Refraction, because the light from the sun is refracting off of the moisture in the air and causing the light rays to bend causing us to see different colors.
Look at the temperature data from the fire truck test again:
TRUCK COLOR SURFACE TEMPERATURE (°F)
BLACK 142°F
BLUE 132°F
RED 128°F
WHITE 113°F
The firefighters want to rank the truck colors from the best choice (absorbs the least heat) to the least best choice (absorbs the most heat) for hot, sunny weather.
Which order shows the best color to the worst color for keeping the truck cool?
A. White → Red → Blue → Black
B. White → Blue → Red → Black
C. Black → Red → Blue → White
D. Red → Blue → White → Black
A. White → Red → Blue → Black
Why can we see a pencil but not air?
Light reflects off the pencil but passes through air without reflection.
Why is the Sun important to our energy sources on Earth?
It provides light and heat energy to help power homes and businesses.
What is an electrical energy transforming into thermal energy example?
The coils of a toaster become hot enough to toast bread.
The burners on an electrical stove heating up when turned on.
Student responses may vary
What happens when a flashlight shines through a prism?
The prism separates white light by refracting colors at different angles.
A fire station is choosing a new fire truck. The station is in a very hot and sunny area, so the firefighters want to pick a truck color that will stay as cool as possible when parked outside in the sun.
They test four trucks that are exactly the same except for their color:
Each truck is parked in direct sunlight for one hour. The firefighters measure the temperature on the surface of each truck after the hour. The results are:
TRUCK COLOR SURFACE TEMPERATURE (°F)
BLACK 142°F
BLUE 132°F
RED 128°F
WHITE 113°F
Based on the data and your knowledge of how colors affect heat absorption, which color truck should the fire station choose to keep the truck coolest, and why?
A. Black, because it absorbs the most light and stays cooler
B. White, because it reflects the most light and absorbs the least heat
C. Red, because it reflects some light but absorbs the most heat
D. Blue, because it is a darker color and warms up faster
B. White, because it reflects the most light and absorbs the least heat
Why can you see yourself in still water but not in rough water?
Smooth water reflects light evenly; rough water scatters it.
Give one example of energy changing forms that you can see at home.
A blender converts electrical energy to mechanical energy.
A tv converts electrical energy to sound and light energy.
Student responses may vary.