What makes an ordinary bar magnet magnetic?
a. Electrons inside it are themselves tiny magnets.
b. The magnetic fields of electrons in the magnet are aligned and add together.
c. It contains magnetic charges.
d. none of the above
a, b
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Which internal energy source is the most important in continuing to heat the terrestrial planets today?
A) accretion B) differentiation C) radioactivity D) tidal heating E) all of the above
The pressure in a liquid depends on liquid
A) density. B) depth. C) both of these D) none of the above
The magnetic field inside a circular loop of wire of radius 30 cm increases at a constant rate from 2.0 × 10^–3 T to 3.5 × 10^–3 T in 0.47 s. If the resistance of the loop is 0.31 ?, what is the current in the loop?
a. 7.4 × 10^–4 A b. 5.8 × 10^–4 A c. 2.9 × 10^–3 A d. 5.8 × 10^–3 A
An automobile engine operates with an overall efficiency of 12%. How much energy is delivered as waste heat (in gallons of gasoline) for each 10 gallons of fuel burned?
a. 1.2 b. 8.8 c. 6.5 d. 4.7 e. 7.5