Electromagnetic Waves — Physics STD 12 Science — Question

For the magnetic field to be maximum due to a small element of current carrying conductor at a point, the angle between the element and the line joining the element to the given point must be

(a) 0°

(b) 90°

(c) 180°

(d) 45°

In metals ____ are the mobile charges.

While a collector to emitter voltage is constant in a transistor, the collector current changes by 8.2 mA when the emitter current changes by 8.3 mA. The value of forward current ratio h_fe is

(a) 82

(b) 83

(c) 8.2

(d) 8.3

When a proton is accelerated through 1V, then its kinetic energy will be

(a) 1840 eV

(b) 13.6 eV

(c) 1 eV

(d) 0.54 eV

Figure (a) shows two capacitors connected in series and joined to a battery. The graph in figure (b) shows the variation in potential as one moves from left to right on the branch containing the capacitors, if

(a)

(b)

(c)

(d) The information is not sufficient to decide the relation between   and

 Identify the electromagnetic wave which is also known as heatwaves.

In R - L - C series circuit, the potential differences across each element is 20V. Now the value of the resistance alone is doubled, then P.D. across R, L and C respectively.

Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Assertion (A): Magnetic moment is measured in joule/ tesla or amp m². Reason (R): Joule/ tesla is equivalent to amp m².

An electron rotating in a circular path of radius r making n revolutions per second. Magnetic moment of electron will be:

Consider a collision between an oxygen molecule and a hydrogen molecule in a mixture of oxygen and hydrogen kept at room temperature. Which of the following are pcssible?

1. The kinetic energies of both the molecules increase.
2. The kinetic energies of both the molecules decrease.
3. The Kinetic energy of the oxygen molecule increases and that of the hydrogen molecule decreases.
4. The kinetic energy of the hydrogen molecule increases and that of the oxygen molecule decreases.