Nuclei — Physics STD 12 Science — Question

A triangular loop of side l carries a current I. It is placed in a magnetic field B such that the plane of the loop is in the direction of B. The torque on the loop is

(a) Zero

(b) IBl

(c)

(d)

Assertion  :   Silicon is preferred over germanium for making semiconductor devices.

Reason      : The energy gap for germanium is more than the energy gap of silicon.

(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 current of two amperes is flowing through a cell of e.m.f. 5 volts and internal resistance 0.5 ohm from negative to positive electrode. If the potential of negative electrode is 10V, the potential of positive electrode will be

(a) 5 V

(b) 14 V

(c) 15 V

(d) 16 V

Between the plates of a parallel plate condenser, a plate of thickness  and dielectric constant  is placed. In the rest of the space, there is another plate of thickness  and dielectric constant . The potential difference across the condenser will be

(a)

(b)

(c)

(d)

A lightning arrester must have the following property.

The figure shows three circuits with identical batteries, inductors, and resistors. Rank the circuits according to the current through the battery (i) just after the switch is closed and (ii) a long time later, greatest first

(a) (i)  (ii)

(b) (i)   (ii)

(c) (i)  (ii)

(d) (i)  (ii)

In the hydrogen atom, an electron makes a transition from n = 2 to n = 1. The magnetic field produced by the circulating electron at the nucleus?

If an electron and a proton have the same de-Broglie wavelength, the K.E of electrons is:

A circular coil of 500 turns of wire has an enclosed area of  per turn. It is kept perpendicular to a magnetic field of induction 0.2 T and rotated by 180° about a diameter perpendicular to the field in 0.1 sec. How much charge will pass when the coil is connected to a galvanometer with a combined resistance of 50 ohms

(a) 0.2 C

(b) 0.4 C

(c) 2 C

(d) 4 C