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Chapter 20 | Electric Current, Resistance, and Ohm's Law
12. The lengths and diameters of three wires are given below. If they all have the same resistance, find the ratio of their resistivities.
Table 20.5
13. Suppose the resistance of a wire is 2 Ω. If the wire is stretched to three times its length, what will be its resistance? Assume that the volume does not change.
20.4 Electric Power and Energy
14.
Figure 20.49 The circuit shown contains a resistor R connected to a voltage supply. The graph shows the total energy E dissipated by the resistance as a function of time. Which of the following shows the corresponding graph for double resistance, i.e., if R is replaced by 2R?
a.
Figure 20.50
b.
Figure 20.51
c.
Figure 20.52
d.
Figure 20.53
15. What will be the ratio of the resistance of a 120 W, 220 V lamp to that of a 100 W, 110 V lamp?
Wire Length Diameter
Wire 1 2 m Wire 2 1 m Wire 3 1 m
1 cm 0.5 cm 1 cm
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