41.

A solid metal sphere of radius 50 cm carries a charge 25 x 10^-10 C, The electrostatic potential at a distance of 20 cm from the centre will be :

• 25 V

• 15 V

• 35 V

• 45 V

Two plates (area = S) charged to + q₁ and + q₂ (q₂ <q₁)are brought closer to form a capacitor of capacitance C. The potential difference across the plates is :

• $\frac{\mathrm{q}1 - \mathrm{q}2}{2\mathrm{C}}$

• $\frac{{\mathrm{q}}_1 - {\mathrm{q}}_2}{\mathrm{C}}$

• $\frac{{\mathrm{q}}_1 - {\mathrm{q}}_2}{4\mathrm{C}}$

• $\frac{2({\mathrm{q}}_1 - {\mathrm{q}}_2)}{\mathrm{C}}$

What is the drift velocity of electrons if the current flowing through a copper wire of 1 mm diameter is 1.1 A. Assume that each atom of copper contributes one electron : (Given: density of Cu = 9 g/cm³ and atomic weight of Cu = 63)

• 0.3 mm/s

• 0.5 mm/s

• 0.1 mm/s

• 0.2 mm/s

A uniform magnetic field is at a right angle to the direction of motion of proton. As a result, the proton describes a circular path of radius 2.5 cm. If the speed of proton is doubled then the radius of the circular path will be :

• 0.5 cm

• 2.5 cm

• 5.0 cm

• 7.5 cm

An electron accelerated through a potential difference enters into a uniform transverse magnetic field and experience a force F. If the accelerating potential is increased to 2V, the electron in the same magnetic field will experience a force :

• F

• F/2

• $\sqrt{2} \mathrm{F}$

• 2F

The certain amount of current when flowing in a properly set tangent galvanometer produces a deflection of 45°. The current be reduced by a factor of ✓3, the deflection would :

• decrease by 30°

• decrease by 15°

• increase by 15°

• increase by 30°

If a current of 3 A fl.owing in the primary coil is reduced to zero in 0.01 s then the induced emf in the secondary coil is 1500 V, the mutual inductance between the two coils is :

• 0.5 H

• 5 H

• 1.5 H

• 10 H

In order to obtain time constant of 10 s in an RC circuit containing a resistance of 10³Ω, the capacity of the condenser should be :

• 10 μF

• 100 μF

• 1000 μF

• 10000 μF

An a-particle, when accelerated through a potential difference of V volt, has a wavelength λ associated with it. In order to have the same λ, by what potential difference a proton must be accelerated?

• 8 V

• 6 V

• 4 V

• 12 V

What is the angle between the electric dipole moment and the electric field strength due to it on the equatorial line?

• 0°

• 90°

• 180°

• None of these