Physics (Part-X) (Railway)

• 1/R = 1/R1 + 1/R2

• So, according to the question, 1/R= ₁/₂ +1/3=(3+2)/6=5/6

• Ω R = 6/5 = 1.2 Ω

• Power = V₂/R

• 540 = (270)²/R

⇒ R = 270 x 270/540  = 72,900/540

= 135 ohm.

d₁ = image distance

m = -d₁/d₀ = -2

d₁ = 1.5 m

1/f = 1/d₀  + 1/1.5 m

1/f = (2/d₀  + 1)/3

3 = (2f +(f * d₀)/d₀

⇒ 2f + (f * d₀)= 3d₀

f(2 + d₀) = 3d₀

F = (3d₀)/(2 + d₀)

Now , m = -d₁ /d₀ ⇒ -2 = 1/5/d₀

⇒ d₀ = -0.75m

1/f = 1/d₀ + 1/d₁

F = (3d₀)/2 +d₀)

= (3 * (-0.75m) /2 -0.75m)

= -1.5 m

• A battery connected to the carbon brushes supplies the current.

d₁ = -20 cm

1/f = 1/d₀  - 1/20 cm

1/f = (20 - d₀) / (20 * d₀)

20 * d₀ = f (20 - d₀

⇒ = (20 * d₀) / d₀ + 20)

d₀ = -20 cm

∴ f = [20 * (-20)] / [(-20) + (20)]

= -20 cm

Therefore, the centre of curvature of the mirror is located at 20 cm from the mirror is  located at 20 cm from the mirrors pole which is equal to the image distance.

• The material of filament must have a high value of melting point so that the filament can withstand the high value of temperature and must not melt.

• It converts motive power (mechanical energy) or fuel-based power (chemical energy) into electric power for use in an external circuit.

• Electric generators work on the principle of electromagnetic induction.

= R ∴ (D/2)²

Diameter = 2 x Radius = 2 x 0.5 mm = 1 mm = 0.001 m length = 100 m

∴ R = ρ l/A

= 2.5 * 10-⁸ * 10²/ π(0.001/2)²

= 2.5 * 4/π = 10/π = ohm.

• Scattering of light depends on the size of particles responsible for scattering.

• The clouds are nearer the earth surface, and they contain dust particle and aggregates of water molecules of sizes bigger than the wavelength of visible light.

• Therefore, the dust particles and water molecules present in clouds scatter all color of incident white light from sun by about the same amount.

• Light of all wavelengths are scattered equally and hence clouds appear white.

• Example: A rainbow is produced by the dispersion of white sunlight by raindrops.