Electric Charges and Fields — Physics STD 12 Science — Question

Which of the following quantities remain constant in a planetary motion (consider elliptical orbits) as seen from the sun?

1. Speed.
2. Angular speed.
3. Kinetic Energy.
4. Angular momentum.

Same as problem 4 except the coil A is made to rotate about a vertical axis (Fig). No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counterclockwise and the coil A is as shown at this instant, t = 0, is:

Nucleus produced due to a-decay of the nucleus   is

(a)

(b)

(c)

(d)

Which of the following properties show that light is a transverse wave?

Copper has face centered cubic (fcc) lattice with interatomic spacing equal to 2.54Å. The value of the lattice constant for this lattice is

(a) 1.27 Å

(b) 5.08 Å

(c) 2.54 Å

(d) 3.59 Å

Assertion  :   A loosely round helix made of stiff wire is suspended vertically with the lower end just touching a dish of mercury. When a current is passed through the wire, the helical wire executes oscillatory motion with the lower end jumping out of and inside of mercury.

Reason     : When electric current is passed through helix, a magnetic field is produced both inside and outside the helix.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

A double convex lens ( having focal length equal to the focal length of a concave mirror. The radius of curvature of the concave mirror is

(a) 10 cm

(b) 20 cm

(c) 40 cm

(d) 15 cm

A straight conductor carries a current. Assume that all free electrons in the conductor move with the same drift velocity v. A and B are two observers on a straight line XY parallel to the conductor. A is stationary. B moves along XY with a velocity v in the direction of the free electrons.

Which of the following is not a mode of radioactive decay

(a) Positron emission

(b) Electron capture

(c) Fusion

(d) Alpha decay

Electromagnetic waves