Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

A radioactive sample of U²³⁸ decay to Pb through a process for which half life is 4.5 × 10⁹ years. The ratio of number of nuclei of Pb to U²³⁸ after a time  of 1.5 × 10⁹ years (given 2^1/3 = 1.26)

(a) 0.12

(b) 0.26

(c) 1.2

(d) 0.37

Two magnets of equal mass are joined at right angles to each other as shown the magnet 1 has a magnetic moment 3 times that of magnet 2. This arrangement is pivoted so that it is free to rotate in the horizontal plane. In equilibrium what angle will the magnet 1 subtend with the magnetic meridian

(a)

(b)

(c)

(d)  0°

A transverse wave travels along the Z-axis. The particles of the medium must move:

1. Along the Z-axis
2. Along the X-axis
3. Along the Y-axis
4. In the X-Y plane.

Holes are created when:

Power factor of LCR circuit in resonance is:

Out of the following, the one whose frequency is minimum is:

Magnitude of potential difference across L. C and R in a series LCR circuit is 100 V. If resistor is re- moved, then magnitude of current in the circuit is:

A charged particle is whirled in a horizontal circle on a frictionless table by attaching it to a string fixed at one point. If a magnetic field is switched on in the vertical direction the tension in the string.

1. Will increase.
2. Will decrease.
3. Will remain the same.
4. May increase or decrease.

For nuclei with A > 100:

What length of the wire of specific resistance 48   is needed to make a resistance of   4.2  (diameter of wire = 0.4 mm)

(a) 4.1 m

(b) 3.1 m

(c) 2.1 m

(d) 1.1 m