The electrostatic field due to a charged conductor just outside the conductor is 

• zero and parallel to the surface at every point inside the conductor

• zero and is normal to the surface at every point inside the conductor

• parallel to the surface at every point and zero inside the conductor

• normal to the surface at every point and zero inside the conductor

A point charge + q is placed at the midpoint of a cube of side a. The electric flux emerging from the cube is

• zero

• $\frac{3 {\mathrm{qa}}^2}{{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• $\frac{{\mathrm{\epsilon }}_0}{4{\mathrm{qa}}^2}$

Figure below shows four plates each of area A and separated from one another by a distance d

What is the capacitance between P and Q ?

• $\frac{{\mathrm{\epsilon }}_0\mathrm{A}}{\mathrm{d}}$

• $\frac{2{\mathrm{\epsilon }}_0\mathrm{A}}{\mathrm{d}}$

• $\frac{3{\mathrm{\epsilon }}_0\mathrm{A}}{\mathrm{d}}$

• $\frac{4{\mathrm{\epsilon }}_0\mathrm{A}}{\mathrm{d}}$

A soap bubble is charged to a potential of 16 V. Its radius is, then doubled. The potential of the bubble now will be

• 16 V

• 8 V

• 4 V

• 2 V

Resistors P and Q are connected in the gaps of the meter bridge. The balancing point is obtained $\frac{1}{3}$ m from the zero end. If a 6 Ω resistance is connected in series with P the balance point shifts to $\frac{2}{3}$ m from the same end. P and Q are

• 4, 2

• 2, 4

• both (a) and (b)

• neither (a) nor (b)

The currents i₁ and i₂ through the resistors R₁ = 10 Ω and R₂ = 30 Ω in the circuit diagram with E₁ = 3 V , E₂ = 3 V and E₃ = 2 V are respectively

• 0.2 A, 0.1 A

• 0.4 A, 0.2 A

• 0.1 A, 0.2 A

• 0.2 A, 0.4 A

77.

An $\mathrm{\alpha }$-particle with a specific charge of 2.5 × 10⁷ C-kg^-1 moves with a speed of 2 × 10⁵ ms^-1 in a perpendicular magnetic field of 0.05 T. Then the radius of the circular path described by it is

• 8 cm

• 4 cm

• 16 cm

• 2 cm

A milliammeter of range O - 30 mA has internal resistance of 20Ω.The resistance to be connected in series to convert it into a voltmeter of maximum reading 3V is

• 49 Ω

• 80 Ω

• 40 Ω

• 30 Ω

A straight conductor of length I carrying a current I, is bent in the form of a semicircle. The magnetic field (in tesla) at the centre of the semicircle is

• $\frac{{\mathrm{\pi }}^2\mathrm{I}}{\mathrm{l}} \times {10}^{-7}$

• $\frac{\mathrm{\pi I}}{\mathrm{l}} \times {10}^{-7}$

• $\frac{\mathrm{\pi I}}{{\mathrm{l}}^2} \times {10}^{-7}$

• $\frac{{\mathrm{\pi I}}^2}{\mathrm{l}} \times {10}^{-7}$

A coil having an inductance of 0.5 H carries a current which is uniformly varying from 0 to 10 A in 2s. The emf (in volts) generated in the coil is

• 10

• 5

• 2.5

• 1.25