Question

Help with 13,14,15 someone

Answer 1

13.

The relationship between power, voltage, and resistance can be expressed as ...

  P = V²/R

Solving for resistance, you find ...

  R = V²/P

Filling in the given values, you get ...

  R = (120 V)²/(360 W) = 40.0 Ω

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14.

⇒ The maximum power the device can dissipate without overheating.

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In practice, the power rating is chosen to meet several requirements, including legal, liability, reliability, life expectancy, and others. For components, there tend to be tradeoffs between power dissipation and reliability. (Higher reliability parts are given a lower power rating even though the process by which they are made is unchanged.) For appliances, there may be legal requirements involving wiring and insurance and fire protection.

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15.

The voltage divider formula is ...

  V₁ = V₀×(R₂/(R₁+R₂))

where R₁ is the series resistor and R₂ is the resistor across which the voltage is being measured. V₀ is the voltage applied across the two resistances.

Filling in your numbers, you get

  V₁ = 25 V × (7.5/(5+7.5)) = 15 V

Answer 2

Thirteen

Formula

W = E^2/R

Solution

R = E^2 /W

R = 120^2 / 360

R = 14400 / 360 = 40.

Answer is A

Fourteen

Another ambiguous question. The acceptable definition used by Electrical Engineers and Mechanical Engineers is what is stated in C. The problem is that B is also a possible answer because it uses the word rate.

And so is A because for safety reasons, you might want to underrate the appliance which guards against any idiot who might overload it "just to see what happens." Hopefully nothing.

I pick C because you don't want to give anything more power than it is rated at or you will destroy it. You are on your own for the right answer. It must be in your notes somewhere. I go with C , but it could easily be A or B and there is no way to distinguish them. Notes, young friend, notes.

Fifteen

The total resistance is 5 + 7.5. = 12.5

The current is E/R = 25 Volts / 12.5 ohms = 2 amps

The voltage drop across the 7.5 ohm resistor is E = I*R

E = 2 * 7.5 = 15 volts.  

Answer: A