The energy required to charge a parallel plate condenser of plate separation d and plate area of cross-section A such that the uniform electric field between the plates is E, is

Three point charges +q, - 2q and +q are placed at points (x = 0, y = a, z = 0), (x = 0, y = 0, z = 0) and (x = a, y = 0, z = 0) respectively. The magnitude and direction of the electric dipole moment vector of this charge assembly are :

•  along +y direction
•  qa along the line joining points
  
  (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

• qa along the line joining points
  
  (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

• qa along the line joining points
  
  (x = 0, y = a, z = 0) and (x = a, y = a, z = 0)

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



This work done in charging fully both the condensers is:

• 2 CV²

• CV²/4

• 3CV²/4

• 3CV²/4

In mass spectrometer used for measuring the masses of ions, the are initially accelerated by an electric potential V and then made to describe semicircular paths of radius R using a magnetic field B. If V and B are kept constant, the ratio  will be proportional to:

• 1/R

• 1/R²

• R²

• R²

Charge +q and -q are placed at points A and B respectively which are distance 2L apart, C is the midpoint between A and B.The work done in moving a charge + Q along the semicircle CED is:

Power dissipated across the 8 Ω resistor in the circuit shown here is 2W. The power dissipated in watt units across the 3 Ω resistor is

• 2.0

• 1.0

• 0.5

• 0.5

An electric dipole of moment  is lying along a uniform electric field  The work done in rotating the dipole by 

• 
• 

• 2pE

• 2pE

A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting thecharging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates

• decreases

• does not change

• becomes zero

• becomes zero

139.

A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system

• Increases by a factor of 4

• Decreases by a factor of 2

• Increases by a factor of 2

• Increases by a factor of 2

The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is

• Independent of the distance between the plates

• Linearly proportional to the distance between the plates

• Inversely proportional to the distance between the plates

• Proportional to the square root of the distance between the plates