Supplementary Problems for PHYS 241
Test 3
1. A copper cylinder has radius 2.0 cm and length 5.0 cm. The initial temperature of the cylinder is 25°C. Look
up the resistivity and the temperature coefficient of resistivity of copper.
a. Wires are connected to the cylinder as shown in Figure 1. What is the
electrical resistance of the cylinder between the wires?
b. If a current of 2.0 A passes through the wires, at what rate is electrical
energy dissipated by the cylinder?
c. What would the resistance of the copper cylinder be if its temperature
rises 100 C°?
2. Consider the schematic shown in Figure 2. Assume two
significant figures for all data.
a. Find the loop current I1 in the loop on the left and the
loop current I2 in the loop in the middle.
b. Find the potential drop across the 10 ohm resistor.
State which side of the resistor is at the higher potential.
c. Find the charge on the capacitor.
3. An initially uncharged capacitor of capacitance 3.30 F is placed across the terminals of a battery with emf
6.20 V. The battery has an internal resistance of 0.200 ohm.
a. Find the formula for the current drawn from the battery as a function of time. What is the time constant of
this circuit?
b. Use calculus and your answer to part a to find the total charge drawn from the battery.
c. Show that your answer to part b is just the final charge of the capacitor (so that charge is conserved).
Figure 1
Figure 2
