Physics
Bats can sense obstacles because they produce

Micro sound waves
Supersonic sound waves
Ultrasonic sound waves
Infrasonic sound waves

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Physics
A transformer

Converts AC voltage to D.C. voltage
Is used to decrease or increase AC voltage
Converts electrical energy into mechanical energy
Converts DC to AC

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Physics
Conservation of energy refers to the fact that

If you conserve energy you will not be as tired
No chemical reaction is 100 percent efficient
The entropy of the universe is always increasing
Energy cannot be created or destroyed but can be converted from one form to another

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