Three charges Q₀, -q and -q are placed at the vertices of an isosceles right angle triangle as in the figure. The net electrostatic potential energy is zero if Q₀ is equal to

• $\frac{\mathrm{q}}{4}$

• $\frac{2\mathrm{q}}{\sqrt{32}}$

• $\sqrt{2\mathrm{q}}$

• + q

42.

In the figure shown below, the terminal voltage across E₂ is

        

• 12 V

• 12.66 V

• 11.34 V

• 11.66 V

The drift velocity of the electrons in a copper wire of length 2 m under the application of a potential difference of 220 V is 0.5 ms^-1. Their mobility (in m²V^-1s^-1)

• 2.5 × 10^-3 

• 2.5 × 10^-2

• 5 × 10²

• 5 × 10^-3

When two resistances R₁ and R₂ are connected in series, they consume 12 W power. When they are connected in parallel, they consume 50 W power. What the ratio of the powers of R₁ and R₂ ?

• 1/4

• 4

• 3/2

• 3

In the circuit shown, if the resistance 5 Ω develops a heat of 42 J per second, heat developed in 2 Ω must be about (in Js^-1)

• 25

• 20

• 30

• 35

When a Daniel cell is connected in the secondary circuit of a potentiometer, the balancing length is found to be 540 cm. If the balancing length becomes 500 cm when the cell is short circuited with 1 Ω, the internal of the cell is

• 0.08 Ω

• 0.04 Ω

• 1.0 Ω

• 1.08 Ω

Two particles of equal charges after being accelerated through the same potential difference enter a uniform transverse magnetic field and describe circular path of radii R₁ and R₂ respectively. Then the ratio of their masses (M₁/M₂)
(M,/M,) i

• $\frac{{\mathrm{R}}_1}{{\mathrm{R}}_2}$

• ${\left(\frac{{\mathrm{R}}_1}{{\mathrm{R}}_2}\right)}^2$

• $\frac{{\mathrm{R}}_2}{{\mathrm{R}}_1}$

• ${\left(\frac{{\mathrm{R}}_2}{{\mathrm{R}}_1}\right)}^2$

Electromagnets are made of soft iron because soft iron has

• low susceptibility and low retentivity

• low susceptibility and high retentivity

• high permeability and low retentivity

• high permeability and high coercivity

Which one of the following characteristics is not associated with a ferromagnetic material ?

• It is strongly attracted by a magnet

• It tends to move from a region of strong magnetic field to a region of low magnetic field

• Its origin is the spin of electrons

• Above the Curie temperature, it exhibits paramagnetic properties

The oscillating frequency of a cyclotron is 10 MHz. If the radius of its dees is 0.5 m, the kinetic energy of a proton, which is accelerated by the cyclotron is

• 10.2 MeV

• 2.55 MeV

• 20.4 MeV

• 5.1 MeV