PHYS142
In Class Assignment #4
Name:
1. If a silver wire has a resistance of 10 Ω at 20˚ C, what is its resistance at 40˚C? (3 pts)
2. Two light bulbs with ratings of 40 W and 100 W are plugged into sockets supplying 120 V.
a) Calculate the resistance of each. Which bulb has the greater resistance? (4 pts)
b) If the 100 W bulb is operated for 2 days and electric energy costs $0.12 per kWh, how
much does it cost?
Convert W to kW. (1 pt)
Multiply by the number of hours to get kWh. (1 pt)
Multiply by cost per kWh. (1 pt)
3. Find the emf of the battery in the circuit below given that the power supplied is 10 W
First, come up with a plan for adding the resistors. Fill in the
blanks below with a P for parallel and an S for series. (4 pts)
Step 1, add the 10.0 Ω and 5.0 Ω resistors in ______
Step 2, add this sum to the 4.00 Ω resistor in ______
Step 3, add this sum to the 3.00 Ω resistor below in
______
Step 4, add this sum to the 3.00 Ω resistor to the left in
_____
Follow the plan above to find the equivalent resistance
for this circuit. (4 pts)
Draw an equivalent circuit showing the single, equivalent resistor. (2 pts)
Find the value of the emf of the circuit given the power consumed and the equivalent resistance. (2
pts)