CBSE-XI-Physics
47: The Special Theory of Relativity
- #21A 100 W bulb together with its power supply is suspended from a sensitive balance. Find the change in the mass recorded after the bulb remains on for 1 year.Ans : Given:
Power of the bulb, P = 100
W = 100 J/s
We know,
Energy = Power × Time
Hence, total energy emitted in 1 year is given by
Etotal= 100 × 3600 × 24 × 365
Etotal= 3.1536 × 109 J
This energy is converted into mass. Thus,
`` \,\mathrm{\,Increase\,}\,\mathrm{\,in\,}\,\mathrm{\,mass\,}=∆m=\frac{{E}_{\,\mathrm{\,total\,}}}{{c}^{2}}=\frac{3.1536\times {10}^{9}}{9\times {10}^{16}}``
`` =3.504\times {10}^{8}\times {10}^{-16}\,\mathrm{\,kg\,}``
`` =3.5\times {10}^{-8}\,\mathrm{\,kg\,}``
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