Wave Motion and Waves on a String — Physics STD 12 Science — Question

A long solenoid has n turns per meter and current I A is flowing through it. The magnetic field at the ends of the solenoid is

(a)

(b)

(c) Zero

(d) 2

Magnetic flux ∅ (in weber) linked with a closed circuit of resistance 10 ohm varies with time t (in seconds) as ∅ =  The induced electromotive force in the circuit at t = 0.2 sec. is

(a) 0.4 volts

(b) – 0.4 volts

(c) – 2.0 volts

(d) 2.0 volts

The stopping potential is directly related to:

Assertion  : Radioactive nuclei emit   particles.

Reason      : Electrons exist inside the nucleus.

(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.

Two lenses of power +12 and – 2 diopters are placed in contact. What will the focal length of combination

(a) 10 cm

(b) 12.5 cm

(c) 16.6 cm

(d) 8.33 cm

The symbol given in figure represents

(a) NPN transistor	(b) PNP transistor
(c) Forward biased PN junction diode	(d) Reverse biased NP junction diode

In the given circuit if point C is connected to the earth and a potential of +2000 V  is given to the point A, the potential at B is

(a) 1500 V

(b) 1000 V

(c) 500 V

(d) 400 V

The charge on electron was discovered by

(a) J.J. Thomson

(b) Neil Bohr

(c) Millikan

(d) Chadwick

Which error is removed when the known and unknown resistances are interchanged in a Meter Bridge?