Some solved questions from CBSE Class 12th Physics Question Paper 2013-Set I, are given here
Q.The motion of copper plate is damped when it is allowed to oscillate between the two poles of a magnet. What is the cause of this damping?
Ans. A continuous change of magnetic flux occurs on the copper plates attached to a pendulum, asit oscillate in the magnetic field between the two poles of the magnet. Hence, eddy currents are set up in the copper plate which tries to oppose the motion of the pendulum, according to the Lenz’s law, and finally bring it to rest.
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Q.Define the activity of a given radioactive substance. Write its S.I unit.
Ans.The rate of disintegration of nucleus with respect to time is called as activity of radioactivity substances.
SI unit is Becquerel (Bq).
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Q.Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations.Name the radiations and write the range of their frequency.
Ans.Welders wear special goggles or face masks with glass windows to protect their eyes from Ultra Violet Rays (UV rays).Frequency range of UV rays is 7.5 x 1014 to 5 x 1017 Hz (800 THz to 30 PHz).