Sound energy is converted into _________ by a microphone?

A. Microwaves

B. Electrical signals

C. Optical Signals

D. Heat energy

(more…)

1 BTU(British thermal unit) is equal to how many joules?

A. 955 joules

B. 990 joules

C. 1055 joules

D. 1211 joules

(more…)

Who invented the battery?

A. Nicolas Carznot

B. Alessandro Volta

C. Michael Faraday

D. George Bessel

(more…)