1. At $0.100 per kW*hr, what does it cost to leave a 40.0 W porch light on day and night for a year?

2. The average television is said to be on 6.3 hours per day. Estimate the yearly cost of electricity to operate 100 million TVs, assuming their power consumption averages 150 W and the cost of electricity averages 11.6 cents/kWh.

3. Part A: With a 1020-W toaster, how much electrical energy is needed to make a slice of toast (cooking time = 1.5 minute)?

Part B: At 12.5 cents/kWh, how much does this cost? (You do not need to enter any units.)

4. An electric water heater consumes 5.60 kW for 2.50 h per day. What is the cost of running it for one year if electricity costs 11.3 cents/kWh?

5. Charge carriers in a semiconductor have a number density n_q = 4.35 10²⁴ carriers m^?3. Each carrier has a charge whose magnitude is that of the electron's charge. If the current density is 8.30 10⁴A/m² what is the average speed of the charge carriers?

6. A copper wire of radius 7.0 mm carries a constant current of 53 A. Find the average drift velocity of the electrons if the density of copper is 9000 kg/m³, assuming one conduction electron per copper atom.

7. Assume that copper has one electron per atom to carry charge. Given that the mass density of copper is 8.9 10³kg/m³ and that its molecular weight is 63.5 g/mol, calculate the drift speed of the electrons in a copper wire that carries 8.40 A and has a circular cross section 0.25 mm in radius.

8. Part A: A 4.25 m length of 2.13 mm diameter wire carries a 765 mA current when 16.8 mV is applied to its ends. If the drift velocity has been measured (by the Hall effect - Section 20-11) to be 1.76E-5 m/s, determine the resistance R of the wire.

Part B: Determine the resistivity ?.

Part C: Determine the number n of free electrons per unit volume.

9. What is the diameter of a 1.44 m length of tungsten wire whose resistance is 0.324 ??

10. In the section of circuit below, R₁ 1.140 ?, R₂ 1.810 ?, and R₃ 0.810 ?. Find the equivalent resistance of this combination of resistors.

R R 3 b RA B C R V R V V R R RR