Lead is a soft, dense metal with a specific heat of 0.028 kcal/kg∙C°, a melting point of
328.0°C, and a heat of fusion of 5.5 kcal/kg. How much heat must be provided to melt a
250.0 kg sample of lead with a temperature of 20.0°C?

What is the function of the commutator in a dc motor? a. to spin the magnet b. to change direct current into alternating current c. to change alternating current into direct current d. to spin the wire coil

Which configuration would produce an electric current? a) rotate a coil of copper wire between two magnets. b) connect a wire between a copper and zinc strip sitting in a beaker of water. c) connect a wire to the (+) positive end of a battery and the other end to a light bulb. d) connect a wire to the negative end of a battery and the other end to a light bulb.

In a classical model of the hydrogen atom, the electron moves around the proton in a circular orbit of radius 0.053 nm. what is the electron's orbital frequency? what is the effective current of the electron?