19. A car's headlight consumes 40 W when on low beam and 50 W when on high beam. (a) Find the current that flows in each case (V = 12 V).

(b) Find the resistance in each case.

21. An electric clothes dryer is rated at 4,000 W. How much energy does it use in 40 min?

23. A clock consumes 2 W of electrical power. How much energy does it use each day?

25. A toaster operating on 120 V uses a current of 9 A. (a) What is the toaster's power consumption? (b) How much energy does it use in 1 min? (c) What is the total resistance of the heating element wires?

27. The generator at a large power plant has an output of 1,000,000 kW at 24,000 V. (a) If it were a DC generator, what would be the current in it?

(b) What is its energy output each dayin joules and in kilowatt-hours?

(c) If this energy is sold at a price of 10 cents per kilowatt-hour, how much revenue does the power plant generate each day?

29. About 40,000 J of energy is stored in a typical 1.5-V D-cell battery. If two such batteries are joined to produce a total of 3.0 V in a flashlight circuit and cause 2.0 A of current to flow through the flashlight bulb, how long will the batteries be able to deliver power to the flashlight at this level?

31. The resistance of an electric heater is 10-ohm when connected to 120 V. How much energy does it use during 30 min of operation?