To make electricity using magnets you need a magnet, wire

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

An atom of lithium-7 has an equal number of(1) electrons and neutrons(2) electrons and protons(3) positrons and neutrons(4) positrons and protons

Ageochemist examines a piece of metal that he found in the soil. he performs tests to identify the metal from its density, electrical conductivity, and melting point. which statement best describes his investigation? a. he is determining physical properties that are sufficient to identify the metal. b. he is determining chemical properties that are sufficient to identify the metal. c. he is determining physical properties that are insufficient to identify the metal. d. he is determining chemical properties that are insufficient to identify the metal.