Model Paper 3 — Physics STD 12 Science — Question

The fundamental frequency of a string is proportional to:

1. Inverse of its length.
2. The diameter.
3. The tension.
4. The density.

In a simple harmonic motion:

1. The potential energy is always equal to the kinetic energy.
2. The potential energy is never equal to the kinetic energy.
3. The average potential energy in any time interval is equal to the average kinetic energy in that time interval.
4. The average potential energy in one time period is equal to the average kinetic energy in this period.

Two metal plates having charges Q, -Q face each other at some separation and are dipped into an oil tank. If the oil is pumped out, the electric field between the plates will:

1. Increase.
2. Decrease.
3. Remain the same.
4. Become zero.

A short sighted person can see distinctly only those objects which lie between 10 cm and 100 cm from him. The power of the spectacle lens required to see a distant object is

(a) + 0.5 D

(b) – 1.0 D

(c)  – 10 D

(d)  + 4.0 D

Two similar spheres having +q  and -q charge are kept at a certain distance. F force acts between the two. If in the middle of two spheres, another similar sphere having +q charge is kept, then it experience a force in magnitude and direction as

(a) Zero having no direction	(b) 8F towards +q  charge
(c) 8F towards -q  charge	(d) 4F towards +q  charge

A charged particle oscillates about its mean equilibrium position with a frequency of 10⁹Hz. The frequency of electromagnetic waves produced by the oscillator is:

When light is refracted, which of the following does not change?

The current through an ideal PN-junction shown in the following circuit diagram will be

(a) Zero

(b) 1 mA

(c) 10 mA

(d) 30 mA

The reading of a high resistance voltmeter when a cell is connected across it is 2.2 V. When the terminals of the cell are also connected to a resistance of 5Ω the voltmeter reading drops to 1.8 V. Find the internal resistance of the cell

(a) 1.2 Ω

(b) 1.3 Ω

(c) 1.1 Ω

(d) 1.4 Ω

K_α  wavelength emitted by an atom of atomic number Z = 11 is λ. Find the atomic number for an atom that emits K_α radiation with wavelength 4l

(a) Z = 6

(b) Z = 4

(c) Z = 11

(d) Z = 44