NEET UG 2011 — Electromagnetism

A charge $Q$ is enclosed by a Gaussian spherical surface of radius $R$. If the radius is doubled, then the outward electric flux will

A coil has resistance $30 \Omega$ and inductive reactance $20 \Omega$ at $50 \mathrm{~Hz}$ frequency. If an $\mathrm{AC}$ source of $200 \mathrm{~V}, 100 \mathrm{~Hz}$, is connected across the coil, the current in the coil will be

A current carrying closed loop in the form of a right angle isosceles triangle $A B C$ is placed in a uniform magnetic field acting along $A B$. If the magnetic force on the $\operatorname{arm} B C$ is $\mathbf{F}$, the force on the arm $A C$ is 

A current of 2 A flows through a $2 \Omega$ resistor when connected across a battery. The same battery supplies a current of 0.5 A when connected across a $9 \Omega$ resistor. The internal resistance of the battery is

A galvanometer of resistance, $G$ is shunted by a resistance $S \mathrm{~ohm}$. To keep the main current in the circuit unchanged, the resistance to be put in series with the galvanometer is

A parallel plate condenser has a uniform electric field $E(\mathrm{~V} / \mathrm{m})$ in the space between the plates. If the distance between the plates is $d(\mathrm{~m})$ and area of each plate is $A\left(\mathrm{~m}^2\right)$ the energy (joule) stored in the condenser is

A short bar magnet of magnetic moment $0.4 \mathrm{~J} \mathrm{~T}^{-1}$ is place in a uniform magnetic field of $0.16 \mathrm{~T}$. The magnet is stable equilibrium when the potential energy is

A square loop, carrying a steady current $I$, is placed in a horizontal plane near a long straight conductor carrying a steady current $I_1$ at a distance $d$ from the conductor as shown in figure. The loop will experience 

A thermocouple of negligible resistance produces an emf of $40 \mu \mathrm{V} /{ }^{\circ} \mathrm{C}$ in the linear range of temperature. A galvanometer of resistance $10 \Omega$ whose sensitivity is $1 \mu \mathrm{A} /$ div, is employed with the termocouple. The smallest value of temperature difference that can be detected by the system will be

A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron

An AC voltage is applied to a resistance $R$ and an inductor $L$ in series. If $R$ and the inductive reactance are both equal to $3 \Omega$, the phase difference between the applied voltage and the current in the circuit is

Charge $q$ is uniformly spread on a thin ring of radius $R$. The ring rotates about its axis with a uniform frequency $f \mathrm{~Hz}$. The magnitude of magnetic induction at the centre of the ring is

Four electric charges $+q,+q,-q$ and $-q$ are placed at the corners of a square of side $2 \mathrm{~L}$ (see figure). The electric potential at point $A$, mid-way between the two charges $+q$ and $+q$, is 

If power dissipated in the $9 \Omega$ resistor in the circuit shown is $36 \mathrm{~W}$, the potential difference across the $2 \Omega$ resistor is 

In an $\mathrm{AC}$ circuit an alternating voltage $e=200 \sqrt{2} \sin 100 t$ volt is connected to a capacitor of capacity $1 \mu \mathrm{F}$. The rms value of the current in the circuit is

In the circuit shown in the figure, if potential at point $A$ is taken to be zero, the potential at point $B$ is 

The current $i$ in a coil varies with time as shown in the figure. The variation of induced emf with time would be 

The electric and the magnetic field, associated with an electromagnetic wave, propagating along the $+z$-axis, can be represented by

The electric potential $V$ at any point $(x, y, z)$, all in metres in space is given by $V=4 x^2$ volt. The electric field at the point $(1,0,2)$ in volt/metre is

The rate of increase of thermo-emf with temperature at the neutral temperature of a thermocouple

The rms value of potential difference $V$ shown in the figure is 

There are four light-weight-rod samples $A, B, C$, $D$ separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted (i) $A$ is feebly repelled (ii) $B$ is feebly attracted (iii) $C$ is strongly attracted (iv) $D$ remains unaffected Which one of the following is true?

Three charges, each $+q$, are placed at the corners of an isosceles triangle $A B C$ of sides $B C$ and $A C, 2 a . D$ and $E$ are the mid points of $B C$ and $C A$. The work done in taking a charge $Q$ from $D$ to $E$ is