A charge + Q, is uniformly distributed within a sphere of radius R. Find the electric field, due to this charge distribution, at a distant point r from the centre of the sphere where :
(i) 0 < r < R
(ii) r > R
Derive an expression for electric field of a dipole at a point on the equatorial plane of the dipole. How does the field vary at large distances?
The charges on two spheres are +7mC and –5mC respectively. They experience a force F. If each of them is given an additional charge of –2mC, the new force of attraction will be
A point charge +Q is placed in the vicinity of a conducting surface. Draw the electric field lines between the surface and the charge.
Figure shows a point charge + Q, located at a distance R/2 from the centre of a spherical metal shell. Draw the electric field lines for the given system.
An electric dipole is held in a uniform electric field.
(i) Show that the net force acting on it is zero.
(ii) The dipole is aligned parallel to the field. Find the work done in rotating it through the angle of 180°.
A charge q is placed at one corner of the cube. The electric flux passing through any one of its face is
Four point charges Q, q, Q and q are placed at the corners of a square of side ‘a’ as shown in the figure.
(i) A point charge (+Q) is kept in the vicinity of an uncharged conducting plate. Sketch electric field lines between the charge and the plate.
(ii) Two infinitely large plane thin parallel sheets having surface charge densities σ₁ and σ₂ (σ₁ > σ₂) are shown in the figure. Write the magnitudes and directions of the fields in the regions marked II and III.
A student connects a cell, of emf E2 and internal resistance r2 with a cell of emf E1 and internal resistance r1, such that their combination has a net internal resistance less than r1. This combination is then connected across a resistance R. Draw a diagram of the 'set-up' and obtain an expression for the current flowing through the resistance.
An inductor L of inductance is connected in series with a bulb B and an ac source. How would brightness of the bulb change when
(i) number of turns in the inductor is reduced,
(ii) an iron rod is inserted in the inductor and
(iii) a capacitor of reactance is inserted in series in the circuit. Justify your answer in each case.
Derive the expression for the average power dissipated in a series LCR circuit for an ac source of a voltage, V = sin ωt , carrying a current,i = sin (ωt + Φ)
Hence define the term “Wattless current”. State under what condition it can be realized in a circuit.
Define an equipotential surface. Draw equipotential surfaces :
(i) in the case of a single point charge and
(ii) in a constant electric field in z-direction. Why the equipotential surfaces about a single charge are not equidistant ?
(iii) Can electric field exist tangential to an equipotential surface ? Give reason.
An electric dipole is placed in a uniform electric field.
(i) Show that no translatory force acts on it.
(ii) Derive an expression for the torque acting on it.
(iii) Find work done in rotating the dipole through 180°.