Multiple Choice QuestionsThe 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 pointsqa 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)
B.
qa along the line joining pointsThe electric dipole moment is a vector quantity directed from negative charge to the similar positive charge.
choose the three coordinate axes as x, y and z and plot the charge with the given coordinates as shown.
O is the origin at which -2q charges is placed. The system is equivalent to two dipoles along x and y- directions respectively. The dipole moments of two dipoles are shown in the figure.
The resultant dipole moment will be directed along OP where P = (a, a, 0).The magnitude of resultant dipole moment is
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
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
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