A. What resistance must be placed in parallel with a 20 ohms resistor to make th

Question

A. What resistance must be placed in parallel with a 20 ohms resistor to make the equivalent resistance, REQ, equal to 15 Ohms?

B. How many joules of energy are required to raise the temperature of 2kg of aluminum from 20 degrees celcius to 200 degrees celcius? (C aluminum =900 J/kg degrees Celsius)

C. Two moles of an ideal gas undergoes an isobaric expansion from 4 liters to 6 liters in a heat engine. If the initial temperature in the gas was 80 degrees celcius, what is the final temperature?

D. A carnot heat engine extracts heat from a reservoir at 250 degrees celcius and does work with an efficient of 32%. What is the temperature of the cold reservoir?

E. A system consisting of an ideal gas in a cylinder fitted with a movable piston absorbs 4000J of heat and does 6000J of work. What is the change in internal energy, deltaE, of the system?

F. An object 3 cm high is placed 20 cm from a convex mirror having a focal length of 8 cm. Find the height of the image.

G. What is the fractional decrease in volume of a solid rubber ball subjected to a pressure of 50.5 x 10^5 Pa? The Bulk Modulus for rubber is 2.4 X 10^9 Pa.

Explanation / Answer

A. 20x/(20+x) = 15

=> x = 60 ohm

B. MC(change in T) = energy

=> energy = 324000 joule

C. V/T = constant

=> 4/353 = 6/T2

=> T2 = 529.5K = 256.3*c

D. 0.32 = 1-(x/523)

=> x = 355.64 K = 82.64*C

E.change in internal energy = 4000 - 6000 = -2000J

F. (1/v) + (1/u) = (1/f)

=> (1/v) +(1/20) = (-1/8)

=> v = -5.714 cm

hi/ho = - v/u

=>hi = 0.857 cm

G. B = P/( fractional decrease in volume )

=>fractional decrease in volume = 50.5 x 10^5 / (2.4 X 10^9 )

= 2.1042 * 10^-3

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