# CBSE Class 12 Physics Solved Model Paper (Set - 2)

May 21, 2015 17:07 IST

The experts at Team Jagran Josh have framed the Model Test Paper for Physics subject which strictly follows the Board pattern of CBSE Class 12 for the year 2016. The Model Test Paper is extremely beneficial for the Class 12 Students appearing for their respective examinations in 2016.

A few Questions from this Model Test Paper are given below:

Q. At an airport, a person is made to walk through the doorway of metal detector, for security reasons. If she/he is carrying anything made of metal, the metal detector emits a sound. On what principle does this work?

Sol. The metal detector works on the principle of resonance in ac circuits. Walking through a metal detector is like, walking' through a coil of many turns- connected to a capacitor turned suitably. If we carry some metal on our body, impedence of the circuit changes, bringing about significant changes in the current. This change in current is detected and the electronic circuit causes an alarm.

Q. Why are the connections between the resistors in a meter bridge made of thick copper strips?

Sol. The resistivity of a copper wire of very low. Also, the connections are thick, so that the area is quite large and hence the resistance of the wires is almost negligible.

Q. Which material is used for the meter bridge wire and why?

Sol. Constantan is used for meter bridge wire because its temperature coefficient of resistance is almost negligible due to which the resistance of the wire does not change with increase in temperature of the wire due to flow of current.

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