Electric Current and Resistance HW

Solutions to Friday Worksheet:

1. 600 C, 600 W.
2. 4 hours, 10 hours
3. 133.3 A
4. A flow of current through one hand and out the other passes through the heart. The current running through the hand and out the elbow would be painful, but not necessarily fatal.
5. Power of the hairdryer is 12,0000J/45 seconds = 266.7 W, voltage = P/I = 88.9 Volts
6. .034 .34 Ohms
7. B, resistance of a cylindrical wire = p*L/A with p = resistivity, L = length of the wire, and A = cross sectional area.
8. 24 Ohms
9. 60/7 Ohms

34. Three lightbulbs.
35. efficiency = 373 W/528 W (1 hp = 746 W. What is the actual power of the motor? What is the electrical power provided to the motor? How can you use efficiency from thermodynamics to relate these two?)