In the diagram, if the current through R1 is 5 A up and if the current through R3 is 3 A up, what is the current in R2?
]
A. 8 A up
B. 8 A down
C. 2 A up
D. 2 A down
E. more information is needed
B. 8 A down
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A solid cylinder is rolling without slipping. What fraction of its kinetic energy is rotational?
A) 1/3 B) 2/3 C) 1/2 D) 1/4 E) 3/4
A +6.0 magnitude star is brighter than a +3.0 magnitude star
Indicate whether the statement is true or false
If body P, with a positive charge, is placed in contact with body Q (initially uncharged), what will be the nature of the charge left on Q?
a. must be greater in magnitude than that on P b. must be equal in magnitude to that on P c. must be negative d. must be positive
A Trombe wall is a masonry wall often used in passive solar homes to store solar energy. Suppose that such a wall, fabricated from 20-cm-thick solid concrete blocks (k = 0.13 W/(mK), ? = 0.05 × 10–5 m2/s) is initially at 15°C in equilibrium with the room in which it is located. It is suddenly exposed to sunlight and absorbs 500 W/m2 on the exposed face. The exposed face loses heat by radiation and convection to the outside ambient temperature of –15°C through a combined heat transfer coefficient of 10 W/(m2 K). The other face of the wall is exposed to the room air through a heat transfer coefficient of 10 W/(m2 K). Assuming that the room air temperature does not change, determine the maximum temperature in the wall after 4 hours of exposure and the net heat transferred to the room.
GIVEN • Trombe wall suddenly exposed to sunlight FIND (a) Maximum temperature in the wall after 4 hours (b) Heat input to the room