What fundamental fact underlies the operation of essentially all electric motors?
A) Iron is the only element that is magnetic.
B) A current-carrying conductor placed perpendicular to a magnetic field will experience a force.
C) Opposite electric charges attract and like charges repel.
D) A magnetic North pole carries a positive electric charge, and a magnetic South pole carries a negative electric charge.
E) Alternating current and direct current are both capable of doing work.
B
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Upon being struck by 240-nm photons, a metal ejects electrons with a maximum kinetic energy of 1.45 eV. What is the work function of this metal? (h = 6.626 × 10-34 J • s, c = 3.00 × 108 m/s, 1 eV = 1.60 × 10-19 J)
A) 3.73 eV B) 3.13 eV C) 4.33 eV D) 4.92 eV
What is the main energy transformation (input and useful output) for a person speeding up while riding a bicycle?
A) kinetic E ? chemical E B) thermal E ? kinetic E C) chemical E ? elastic E D) elastic E ? kinetic E E) chemical E ? kinetic E
The isotope, tritium, has a half-life of 12.3 years. Assume we have 10 kg of the substance. How much tritium will be left after 30 years?
a. 0.20 kg b. 1.8 kg c. 0.18 kg d. 1.7 kg e. 4.1 kg
What is a diffraction grating?