chapter four questions

Question

A microwave oven has a power requirement of 1,254 W. A frozen dinner requires 5.1 min to heat on full power.

(a) How much electrical energy (in kWh) is used?

 kWh

(b) If the cost of electricity is 11¢ per kWh, how much does it cost to heat the dinner? (Do not round your final answer. Fractional cent values are acceptable.)

 

Answer 1

Hello Yvette K.,

You may want to take note, that the power requirement of the oven does NOT all go into heating the food. Some power is taken by the carousel motor, and some is wasted or trapped if not used by the oven. Older ovens (with a large top compartment) have a trap ("microwave dump"); newer ovens (without a large top compartment, they usually say "Inverter" on the name) rely on having some watery material in the oven, and if you operate them dry you will presently blow the generator out.

By the way, both (a) and (b) are simple multiplications. Just pay attention to your units, and use conversion factors as needed (e.g., * (1 hr / 60 min)).

Wyzant Ask-an-Expert is not a spreadsheet for solving your homework set. That's 7 problems at once on the same skill set, using physics equations for forces, energies, masses, momenta, and so on. That's spamming. Please limit yourself to a single problem, get the technique from the answer, and apply it yourself from there on. If you are totally at sea on applying equations to problems, please find some one-on-one tutoring; Wyzant makes that possible, or perhaps your peers, family, friends, etc..

-- Cheers, -- Mr. d.