SP212/3321&5521
Chapter 26 - Worksheet #2
Question 1: A 12.0 Ω resistor is connected to a 15.0 V battery. How long does it take for 4.22 kJ of
heat to be dissipated by the resistor?
Question 2: A sample of germanium has a resistivity of 0.60 Ω·m. This material forms a rectangular
box that is 18 cm × 3.5 mm × 3.5 mm (18 cm long, 3.5 mm wide, and 3.5 mm high). (a) What is
the resistance of this box measured across its length? (b) Suppose that you have two identical boxes
as described above. What is the total resistance across its length if you connect them along a small
face (yielding a sample with a total length of 36 cm)? (c) Suppose instead that you connect them
along a large face, yielding a total sample of 18 cm × 7.0 mm × 3.5 mm. What is the resistance
now, again measured across the length?
SP212/3321&5521
Chapter 26 - Worksheet #2
Question 3: A hair dryer is designed to dissipate energy at 1300 W when plugged into a 120 V outlet.
(a) What is the resistance of the hair dryer? (b) What current runs through it when it is operating?
Question 4: The resistivity of aluminum is 2.65×10−8 Ω·m. An aluminum wire has a circular cross
section, but the diameter changes as shown below. The left half has a diameter of 0.11 mm while
the right half has a diameter of 0.22 mm. Each half is 75 cm long. A potential difference of 1.5 V is
applied across this wire. (a) How much current flows through the wire? (The total resistance is the
sum of the resistance in each half.) (b) What is the magnitude of the current density in each half?
(c) What is the electric field magnitude in each half?
75 cm
0.11 mm
0.22 mm
75 cm