question 1
(CTFSC) A physics teacher, in a class on resistors and their applications, asks his students what they could do to get hotter water from their electric showers. Several answers emerged, and only one was correct. Check the correct answer given by the student.
a) We can decrease the length of the resistor. With that, we would increase the electrical current and, consequently, we would have more electrical energy transformed into heat.
b) We can increase the length of the resistor. With that, we would increase the electrical current and, consequently, we would have more electrical energy transformed into heat.
c) We can decrease the cross-sectional area of the resistor. With that, we would increase the electrical current and, consequently, we would have more electrical energy transformed into heat.
d) We can increase the length of the resistor. With that, we would decrease the electric current and, consequently, we would have more electric energy transformed into heat.
e) We can increase the resistivity of the resistor material. With that, we would increase the electrical current and, consequently, we would have more electrical energy transformed into heat.
question 2
(Enem - 2010) The electrical resistance of a wire is determined by its dimensions and the structural properties of the material. The conductivity (σ) characterizes the structure of the material, in such a way that the resistance of a wire can be determined by knowing L (wire length) and THE (the cross-section area). The table lists the material with its respective resistivity at room temperature.
Material |
Conductivity (S.m/mm2) |
Aluminum |
34,2 |
Copper |
61,7 |
Iron |
10,2 |
Silver |
62,5 |
Tungsten |
18,8 |
Keeping the same geometric dimensions, the wire that has the lowest electrical resistance is the one made of:
a) tungsten
b) aluminum
c) iron
d) copper
e) silver
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