Question

A tungsten lamp is at 3000 K and its surface area is 0.3 cm2. The emissivity found experimentally for tungsten lamp is 0.4. The rate at which heat is radiated from lamp is proportional to?​

Answer 1

Given info : A tungsten lamp is at 3000 K and its surface area is 0.3 cm2. The emissivity found experimentally for tungsten lamp is 0.4.

To find : The rate at which heat is radiated from lamp is ..

solution : emissivity, e = 0.4

Temperature of Tungsten lamp, T = 3000 K

surface area, A = 0.3 cm² = 0.3 × 10¯⁴ m²

rate at which heat is radiated from lamp , Q = eAσT⁴

here σ is Stefan's Boltzmann's constant. i.e., 5.6 × 10^-8 W/m²K⁴

now, Q = 0.4 × 0.3 × 10¯⁴ × 5.6 × 10^-8 × (3000)⁴

= 54.432 Watt

Therefore the rate at which heat is radiated from lamp is 54.432 Watt.

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