Alternating Current — Physics STD 12 Science — Question

In case of linearly polarized light, the magnitude of the electric field vector :

(a) Does not change with time

(b) Varies periodically with time

(c) Increases and decreases linearly with time

(d) Is parallel to the direction of propagation

The number of turns of primary and secondary coils of a transformer are 5 and 10 respectively and the mutual inductance of the transformer is 25 henry. Now the number of turns in the primary and secondary of the transformer are made 10 and 5 respectively. The mutual inductance of the transformer in henry will be

(a) 6.25

(b) 12.5

(c) 25

(d) 50

Assertion : V-i characteristic of P-N junction diode is same as that of any other conductor.

Reason     : P-N junction diode behave as conductor at room temperature.

(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 thin metal plate P is inserted half way between the plates of a parallel plate capacitor of capacitance C in such a way that it is parallel to the two plates. The capacitance now becomes

(a) C

(b) C/2

(c) 4C

(d) None of these

The graph between the instantaneous concentration (N)  of a radioactive element and time (t)  is

(a)

(b)

(c)

(d)

A charge is brought from a point on the equatorial plane of a dipole to its mid-point. Which of the following quantities remains constant?

An electron with kinetic energy 5eV is incident on a hydrogen atom in its ground state. The collision:

If L is the coherence length and c the velocity of light, the coherent time is

(a) cL

(b)

(c)

(d)

If light is passed through a double-slit opening and falls onto a screen, Identify the pattern produced on the screen.

The tangent at any point of  field line gives the direction of: