Two identical conducting balls A and B have positive charges q₁ and q₂ respectively. But q₁ ≠ q₂. The balls are brought together so that they touch each other and then kept in their original positions. The force between them is

• less than that before the balls touched

• greater than that before the balls touched

• same as that before the balls touched

• zero

142.

A positively charged ball hangs from a silk thread. we put a positive test charge q_o at a point and measure F/q_o, then it can be predicted that the electric field strength E

• >F/q_o

• =F/q

• <F/q_o

• Cannot be estimated

Capacitor C₁ of capacitance 1μF and capacitor C₂ of capacitance 2 μF are separately charged fully by a common battery. The two capacitors are then separately allowed to discharged through equal resistors at time t =0

• the current in each of the two discharging circuits is zero at t = 0

• the currents in the two discharging circuits at  t= 0 are equal but non-zero

• the currents in the two discharging circuits at t=0

• Capacitor C₁ loses 40% of its initial charge sooner than _C2 loses 40% of the initial charge.

Two condensers, one of capacity C and the other of capacity C/2, are connected to a V- volt battery, as shown.

The work done in charging fully both the condensers is

• CV²

• $\frac{1}{4}{\mathrm{CV}}^2$

• $\frac{3}{4}{\mathrm{CV}}^2$

• $\frac{1}{2}{\mathrm{CV}}^2$

A capacitor of capacitance 5μF is connected as shown in the figure. The internal resistance of the hell is 0.5 Ω. The amount of charge on the capacitor plates is

• 80μC

• 40 μC

• 20 μC

• 10μC

Two metal plates having a potential difference of 800 V and 2 cm apart. It is found that a particle of mass 1.96 x 10^-15 kg remaining suspended in the region between the plates. The charge on the particle must be (e = elementry charge)

• 8e

• 6e

• 3e

• 2e

The working of dynamic is based on the principle of

• Electromagnetic induction

• chemical effect of current

• magnetic effect of current

• heating effect of current

 The capacity of a parallel plate capacitor with no dielectric substance but with a separation of 0.4 cm is 2µF. The separation is reduced to half and it is filled with a dielectric substance of value of 2.8. The final capacity of capacitor is

• 15.6μF

• 11.2μF

• 19μF

• 22.4μF

The plates of a parallel plate capacitor of capacity of 50 µF are charged by a battery to a potential of 100 volt. The battery remains connected the plates are separated from each other so that the distance between them is doubled. Then, the energy spent by battery in doing so, will be

• $12.5\times {10}^{-2}\mathrm{J}$

• $35\times {10}^{-2}\mathrm{J}$

• 42.5×10^-2J

• 25×10^-2J

Two small magnets each of magnetic moment 10 Am² are placed in end on position 0.1 m apart from their centres. The force acting between them is

• 0.6N

• 0.06N

• 0.06×10⁷N

• 0.6×10⁷N