﻿ Name the physical quantity which remains same for microwaves of

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## CBSE Class 12 Physics Solved Question Paper 2012

1.

When electrons drift in a metal from lower to higher potential, does it mean that all the free electrons of the metal are moving in the same direction?

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2.

The horizontal component of the earth’s magnetic field at a place is B and angle of dip is 60°.

What is the value of vertical component of earth’s magnetic field at equator?
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3.

Show on a graph, the variation of resistivity with temperature for a typical semiconductor.

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4.

Why should electrostatic field be zero inside a conductor?

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# 5.Name the physical quantity which remains same for microwaves of wavelength 1 mm and UV radiations of 1600 Å in vacuum.

Both microwaves and UV radiations are EM waves. Therefore, their speed ( c = ) will remain same in vacuum.

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6.

Predict the directions of induced currents in metal rings 1 and 2 lying in the same plane where current I in the wire is increasing steadily.

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7.

A cell of emf E and internal resistance r is connected to two external resistances R1 and R2 and a perfect ammeter. The current in the circuit is measured in four different situations:

(i) without any external resistance in the circuit.

(ii) with resistance R1 only

(iii) with R1 and R2 in series combination

(iv) with R1 and R2 in parallel combination.

The currents measured in the four cases are 0.42 A, 1.05 A, 1.4 A and 4.2 A, but not necessarily in that order. Identify the currents corresponding to the four cases mentioned above.
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8.

The susceptibility of a magnetic material is –2.6 × 10–5. Identify the type of magnetic material and state its two properties.

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9.

Two identical circular wires P and Q each of radius R and carrying current ‘I’ are kept in perpendicular planes such that they have a common center as shown in the figure. Find the magnitude and direction of the net magnetic field at the common center of the two coils.

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10.

When an ideal capacitor is charged by a dc battery, no current flows. However, when an ac source is used, the current flows continuously. How does one explain this, based on the concept of displacement current?

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