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Find the value of the unknown resistance in each case:
a. A 20 Ω, 18 Ω, and an unknown resistor connected in series to give a total resistance of 64 Ω.
b. Two identical unknown bulbs connected in series with 50 Ω and a 64 Ω heater to produce a total resistance of 150 Ω.
Find the total resistance in each of the cases:
a) Three 30 Ohm light bulbs and two 20 Ohm heating elements connected in a series.
b) Two strings of Christmas tree lights if the first string has eight 4 Ohm bulbs in series and the second has twelve 3 Ohm bulbs in series.
A 100 W lamp has steady current of 0.83 A in its filaments. How long is required for 1 mol electrons to pass through the lamp?
The earth revieved about 1300W/m^2 energy from the sun. Assuming the energy to be in the form of plane polarized monochromatic waves and assuming Normal incidence, calculate
1. The magnitude of the electric filed vector
2. The magnitude of the magnetic field vector
A bird flies 5km on a bearing of 35. How fast north and east of it's starting point is it's final position.
Consider gallium arsenide at T=300 K, assume the photon intensity at a particular point is I(x)=
0.05 W/cm2 at a wavelength of 0.75 m. The absorption coefficient at this wavelength is 0.9x104
cm-1
.
(a) Calculate the generation rate of electron hole pairs.
(b) Calculate the steady state excess concentration of electrons if the minority carrier (hole)
life time is 10-7
sec.
A force of 20N act on an object of an angle 30degrees to the inclined plane. If the object moves 8metres up the plane
(a) What is the effective force that moves the object up the plane
(b) what is the work done to move the object up the plane
1. Using the Weiszacker’s formula, calculate the binding energy per nucleon for 235
92 U and
its two fission products: 149
60 Nd and 86
32Ge.
In the Helium-Neon laser, lasing occurs between two excited states of the neon atom. However, in many lasers lasing occurs between the ground state and an excited state. Consider such a laser that emits at wavelength λ = 550 nm. If a population inversion is not generated, (i) what is the ratio of the population of atoms in state Ex to the population in the ground state E0 with atoms at room temperature? For the condition in (i), at (ii) what temperature would the ratio Nx/N0 be 1/2?.
7. The atomic ratio between Uranium isotope 238U and 234U in a mineral sample is found to be 1.8 × 104 . The half-life of 234U is 2.5 × 105 yrs. Find the hal-life of 238U.
