The superconducting magnet in a magnetic resonance imaging system consists of a solenoid with 5.6 H of inductance. The solenoid is energized by connecting it to a 1.2 V DC power supply. Starting from zero, how long does it take for the solenoidto reach its operating current of 100 A?

466.67 s or 7.78 min

Explanation:

Applying,

E = LdI/dtEquation 1

Where E = Energized E.m.f in the solenoid, dI = change in current, dt = change in time.

make dt the subject of the equation,

dt = Ldi/E Equation 2

Given: L = 5.6 H, dI = 100-0 = 100 A, E = 1.2 V

Substitute into equation 2

dt = 5.6(100)/1.2

dt = 560/1.2

dt = 466.67 s

dt = (466.67/60) min = 7.78 min

Hence, it takes 466.67 s or 7.78 min for the solenoid to reach its operating current.

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(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.