Magnetism And Matter — Physics STD 12 Science — Question

A closed surface S is constructed around a conducting wire connected to a battery and a switch (figure). As the switch is closed, the free electrons in the wire start moving along the wire. In any time interval, the number of electrons entering the closed surface S is equal to the number of electrons leaving it. On closing the switch, the flux of the electric field through the closed surface:

1. Is increased.
2. Is decreased.
3. Remains unchanged.
4. Remains zero.

Two unlike charges of magnitude q are separated by a distance 2d. The potential at a point midway between them is

(a) Zero

(b)

(c)

(d)

As per this diagram a point charge +q is placed at the origin O. Work done in taking another point charge -Q  from the point A [co-ordinates (0, a) ] to another point B [co-ordinates (a, 0)] along the straight path AB is

(a) Zero

(b)

(c)

(d)

A charged particle moving in a magnetic field experiences a resultant force

(a) In the direction of field

(b) In the direction opposite to that field

(c) In the direction perpendicular to both the field and its velocity

(d) None of the above

The current in the following circuit is

(a)

(b)

(c)

(d) 1A

There is some liquid in a closed bottle. The amount of liquid is continuously decreasing. The vapour in the remaining part:

1. Must be saturated.
2. Must be unsaturated.
3. May be saturated.
4. There will be no vapour.

For a thermocouple, the neutral temperature is 270℃ and the temperature of its cold junction is 20℃. If there is no deflection in the galvanometer, the temperature of the hot junction should be

(a) 210 ℃

(b) 540 ℃

(c) 520 ℃

(d) 209 ℃

The energy of a given sample of an ideal gas depends only on its:

1. Volume.
2. Pressure.
3. Density.
4. Temperature.

Potential gradient is defined as

(a) Fall of potential per unit length of the wire

(b) Fall of potential per unit area of the wire

(b) Fall of potential per unit area of the wire

(d) Potential at any one end of the wire