The resistance of a wire at 300 K is found to be 0.3 2. If  the temperature coefficient of resistance of wire is 1.5 x 10^-3 K^-1, the temperature at which the resistance becomes 0.6 Ω is

• 720 K

• 345 K

• 993 K

• 690 K

A resistor and a capacitor are connected in series with an AC source. If the potential drop across the capacitor is 5 V and that across resistor is 12 V, then applied voltage is

• 13 V

• 17 V

• 5 V

• 12 V

A galvanometer of resistance 240 Ω allows only 4% of the main current after connecting a shunt resistance. The value of the shunt resistance is

• 10 Ω

• 20 Ω

• 8 Ω

• 5 Ω

An α-particle of mass 6.4 x 10^-27 kg and charge 3.2 x 10^-19 C is situated in a uniform electnc field of 1.6 x 10⁵ Vm^-1. The velocity of the particle at the end of 2 ×10^-2 m path when it starts from rest is

• $2\sqrt{3} \times {10}^5 {\mathrm{ms}}^{-1}$

• 8 × 10⁵ ms^-1

• 16 × 10⁵ ms^-1

• $4\sqrt{2} \times {10}^5 {\mathrm{ms}}^{-1}$

35.

The charge deposited on 4 µF capacitor in the circuit is

              

• 6 × 10^-6 C

• 12 × 10^-6 C

• 24 × 10^-6 C

• 36 × 10^-6 C

A coil of n number of turns is wound tightly in the form of a spiral with inner and outer radii a and b respectively. When a current of strength is passed through the coil, the magnetic field at its centre is

• $\frac{{\mathrm{\mu }}_0\mathrm{nI}}{\left(\mathrm{b} - \mathrm{a}\right)} {\log }_{\mathrm{e}} \frac{\mathrm{a}}{\mathrm{b}}$

• $\frac{{\mathrm{\mu }}_0\mathrm{nI}}{2\left(\mathrm{b} - \mathrm{a}\right)}$

• $\frac{2 {\mathrm{\mu }}_0\mathrm{nI}}{\mathrm{b}}$

• $\frac{{\mathrm{\mu }}_0\mathrm{nI}}{2\left(\mathrm{b} - \mathrm{a}\right)} {\log }_{\mathrm{e}} \frac{\mathrm{b}}{\mathrm{a}}$

The electric potential at any point x, y,z in metres is given by V = 3x². The electric field at a point (2, 0, 1) is

• 12 Vm^-1

• − 6 Vm^-1

• 6 Vm^-1

• − 12 Vm^-1

Near a circular loop of conducting wire as shown in the figure an electron moves along a straight line. The direction of the induced current if any in the loop is

• variable

• clockwise

• anti-clockwise

• zero

The magnetic dipole moment of a current loop is independent of

• magnetic field in which it is lying

• number of turns

• area of the loop

• current in the loop

In ruby laser, the stimulated emission is due to transition from

• metastable state to any lower state

• any higher state to lower state

• metastable state to ground state

• any higher state to ground state