Energy is transferred in solids by conduction, which means that a) heat travels in both directions. b) heat travels from the cooler object to the hotter object. c) heat travels from the hotter object to the cooler object. d) heat does not travel between objects of different temperatures. 28) when a student combed his dry hair for a long time, his hair began to stand up. which of these has most likely happened? a) the comb and hair have become charged with similar charges. b) the comb and hair have become charged with opposite charges. c) the comb has become charged, but the hair has remained neutral. d) the hair has become charged, but the comb has remained neutral. 29) why does earth orbit the sun rather than any other body in the solar system? a) the mutual repulsions among all the planets hold earth in its orbit. b) the earth is closer to the sun than other bodies in the solar system. c) the sun is the most massive object; gravitational attraction is related to mass. d) the rotational motions of all the planets, including earth, cause them to remain in its orbit around the sun. 30) which change would result in a stronger electromagnet? a) reducing the number of batteries b) increasing the voltage of the battery c) substituting another metal for the iron core d) decreasing the number of coils around the iron core.