Find the resistance (in Ω) that must be placed in parallel with a 25.0 Ω galvanometer having a 50.0 µA sensitivity (the same as the one discussed in the text) to allow it to be used as an ammeter with a 540 mA full-scale reading.

2.315×10⁻³ Ω

Explanation:

To convert a galvanometer to an ammeter, a low resistance (Shunt) is connected in parallel to the galvanometer.

From the question,

Voltage across the parallel resistor = voltage across the resistance of the galvanometer.

From ohm's law,

Voltage = Current×Resistance.

I'R' = IR Equation 1

Where I' = current flowing through the galvanometer, R' = Resistance of the galvanometer, I = current flowing through the the parallel resistor, R = Resistance of the parallel resistor.

make R the subject of the equation

R = I'R'/I Equation 2

Given: I' = 50 μA = 50×10⁻⁶ A, R' = 25 Ω, I = (540 mA -  50 μA) = 0.54 - 0.00005 = 0.53995 A.

Substitute into equation 2

R = 50×10⁻⁶(25)/0.53995

R = 2.315×10⁻³ Ω

Hence the the resistance in parallel = 2.315×10⁻³ Ω

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(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.

pecialized keyboards