Physics Electromagnetism questions from JEE Main 2005.
A charged ball B hangs from a silk thread $S$ which makes an angle $\theta$ with a large charged conducting sheet $\mathrm{P}$, as show in the figure. The surface charge density $\sigma$ of the sheet is proportional to 
A charged particle of mass $\mathrm{m}$ and charge $q$ travels on a circular path of radius $r$ that is perpendicular to a magnetic field $\mathrm{B}$. The time taken by the particle to complete one revolution is
A circuit has a resistance of $12 \Omega$ and an impedance of $15 \Omega$. The power factor of the circuit will be
A coil of inductance $300 \mathrm{mH}$ and resistance $2 \Omega$ is connected to a source of voltage 2V. The current reaches half of its steady state value in
A fully charged capacitor has a capacitance ' $C$ ' it is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity ' $s$ ' and mass ' $\mathrm{m}$ '. If the temperature of the block is raised by ' $\Delta \mathrm{T}$ '. The potential difference $V$ across the capacitance is
A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be
A magnetic needle is kept in a non-uniform magnetic field. It experiences
A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be
A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is C then the resultant capacitance is
A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected along the direction of the fields with a certain velocity then
An energy source will supply a constant current into the load of its internal resistance is
In the circuit, the galvanometer $G$ shows zero deflection. If the batteries $A$ and $B$ have negligible internal resistance, the value of the resistor $\mathrm{R}$ will be 
One conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field $B$ is perpendicular to the plane of the figure. if each tube moves towards the other at a constant speed V, then the emf induced in the circuit in terms of $B, \ell$ and $\mathrm{V}$ where $\ell$ is the width of each tube will be 
The phase difference between the alternating current and emf is $\pi / 2$. Which of the following cannot be the constituent of the circuit?
The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of $100 \mathrm{~W}$ and $200 \mathrm{~V}$ lamp when not in use?
The self inductance of the motor of an electric fan is $10 \mathrm{H}$. In order to impart maximum power at $50 \mathrm{~Hz}$, it should be connected to a capacitance of
Two concentric coils each of radius equal to $2 \pi \mathrm{cm}$ are placed at right angles to each other. 3 Ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic induction in Weber $/ \mathrm{m}^2$ at the centre of the coils will be $\left(\mu_0=4 \pi \times 10^{-7}\right.$ Wb/A-m)
Two point charges $+8 q$ and $-2 q$ are located at $x=0$ and $x=L$ respectively. The location of a point on the $x$ axis at which the net electric field due to these two point charges is zero is
Two sources of equal emf are connected to an external resistance R. The internal resistance of the two sources are $R_1$ and $R_2\left(R_2>R_1\right)$. If the potential difference across the source having internal resistance $\mathrm{R}_2$ is zero, then
Two thin, long parallel wires separated by a distance 'd' carry a current of 'i' $A$ in the same direction. They will
Two thin wires rings each having a radius $R$ are placed at a distance $d$ apart with their axes coinciding. The charges on the two rings are $+q$ and $-q$. The potential difference between the centres of the two rings is
Two voltameters one of copper and another of silver, are joined in parallel. When a total charge $q$ flows through the voltameters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are $z_1$ and $z_2$ respectively the charge which flows through the silver voltameter is