Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. What is the magnitude of the magnetic field midway between the two wires? (?0 = 4? × 10-7 T ? m/A)
A) 2.0 × 10-5 T
B) 4.0 × 10-5 T
C) 1.0 × 10-5 T
D) 3.0 × 10-5 T
E) 5.0 × 10-5 T
E
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If the energy of n = 6 is –0.378 eV and that of n = 4 is –0.850 eV in a hydrogen atom, a transition from n = 6 to n = 4 will emit a photon of what energy?
An airplane flies in a semi-circular arc in order to simulate “weightlessness” for its occupants. If the radius of the semicircular path it flies is 3500 m, what is the speed at which the plane flies?
A. 357 m/s B. 580 m/s C. 185 m/s D. 1180 m/s
The limiting level below which a stream cannot erode the land is called its
a. base level. b. ultimate level. c. bed level. d. erosion level.
Two 1.5 m-square and parallel flat plates are 30 cm apart. Plate A1 is maintained at a temperature of 1100 K and A2 at 500 K. The emissivities of the plates are 0.5 and 0.8, respectively. Considering the surroundings black at 0 K and including multiple inter-reflections, determine (a) the net radiant exchange between the plates and (b) the heat input required by surface A1 to maintain its temperature. The outer-facing surfaces of the plates are adiabatic.
GIVEN
? Two square parallel flat plates, 30 cm apart
? Temperature of A1 (T1) = 1100 K
? Temperature of A2 (T2) = 500 K
? Emittances: ?1 = 0.5 ?2 = 0.8
? Surroundings are black at (T3) = 0 K
FIND
Including multiple inter-reflections, determine:
(a) The net radiant exchange (q1–2)
(b) The heat input at surface A1 (q1) required to maintain its temperature
SKETCH
PROPERTIES AND CONSTANTS
