Magnetism And Matter — Physics STD 12 Science — Question

To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because

(a) Determination of moment of inertia is not needed which minimises the errors

(b) Less observations are required

(c) Comparatively less calculations

(d) All the above

Two PN-junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be

(a) In the circuit (1) and (2)	(b) In the circuit (2) and (3)
(c) In the circuit (1) and (3)	(d) Only in the circuit (1)

Assertion  : The electromagnetic waves of shorter wavelength can travel longer distances on earth's surface than those of longer wavelengths.

Reason      :  Shorter the wavelength, the larger is the velocity of wave propagation.

(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.

Which of the following pairs represent units of the same physical quantity?

1. Kelvin and joule.
2. Kelvin and calorie.
3. Newton and calorie.
4. Joule and calorie.

The minimum distance between an object and its real image formed by a convex lens is

(a) 1.5 f

(b) 2 f

(c) 2.5 f

(d) 4 f

When the momentum of a proton is changed by an amount P₀, the corresponding change in the de-Broglie wavelength is found to be 0.25%. Then, the original momentum of the proton was

(a) p0

(b) 100 p0

(c) 400 p0

(d) 4 p0

Which of the following statement is incorrect

(a) Both ac and dc dynamo have a field magnet

(b) Both ac and dc dynamo have an armature

(c) Both ac and dc dynamo convert mechanical energy into electrical energy

(d) Both ac and dc dynamo have slip rings

Predict the effect of temperature of the conductor on the drift velocity of electrons.

Assertion  :   To protect any instrument from external magnetic field, it is put inside an iron body.

Reason      : Iron is a magnetic substance.

(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.