Electromagnetism PYQ — Page 8

A wire of length $L$ metre carrying a current of $I$ ampere is bent in the form of a circle. Its magnetic moment is,

A $40\mu F$ capacitor is connected to a $200V$, $50\mathrm{Hz}$ AC supply. The rms value of the current in the circuit is, nearly:

Which of the following graph represents the variation of resistivity $(\rho )$ with temperature $(T)$ for copper?

For the circuit given below, the Kirchhoff's loop rule for the loop $BCDEB$ is given by the equation 

For the circuit shown in the figure, the current $I$ will be 

A series$LCR$ circuit is connected to an ac voltage source. When $L$ is removed from the circuit, the phase difference between current and voltage is $\frac{\pi }{3}$. If instead $C$ is removed from the circuit, the phase difference is again $\frac{\pi }{3}$ between current and voltage. The power factor of the circuit is:

Two toroids 1 and 2 have total number of turns 200 and 100 respectively with average radii $40 \mathrm{~cm}$ and $20 \mathrm{~cm}$ respectively. If they carry same current $i$, the ratio of the magnetic fields along the two loops is

A cylindrical conductor of radius $R$ is carrying a constant current. The plot of the magnitude of the magnetic field $B$ with the distance $d$ from the centre of the conductor is correctly represented by the figure.

A $800$ turn coil of the effective area $0.05 {m}^{2}$ is kept perpendicular to the magnetic field $5\times {10}^{-5} T.$ When the plane of the coil is rotated by ${90}^{o}$ around any of its coplanar axis in $0.1 s,$ the emf induced in the coil will be:

A cycle wheel of radius $0.5 \mathrm{~m}$ is rotated with constant angular velocity of $10 \mathrm{rad} / \mathrm{s}$ in a region of magnetic field of $0.1 \mathrm{~T}$ which is perpendicular to the plane of the wheel. The EMF generated between its centre and the rim is

Two parallel infinite line charges with linear charge densities $+\lambda C{m}^{-1}$ and $-\lambda C{m}^{-1}$ are placed at a distance of $2R$ in free space. What is the electric field mid-way between the two-line charges?

Two point charges A and B, having charges $+Q$ and $-Q$ respectively, are placed at certain distance apart and force acting between them is $F$. If $25%$ charge of $A$ is transferred to $B$, then the force between the charges becomes

Which of the following acts as a circuit protective device?

A hollow metal sphere of radius $R$ is uniformly charged. The electric field due to the sphere at a distance $r$ from the center

In which of the following devices, the eddy current effect is not used?

The meter bridge shown in the balance position with $\frac{\mathrm{P}}{\mathrm{Q}}=\frac{\mathrm{l}_1}{\mathrm{l}_2}$. If we now interchange the positions of galvanometer and cell, will the bridge work? If yes, that will be balanced condition? 

For a transparent medium relative permeability and permittivity $\mu_{\mathrm{r}}$ and $\epsilon_{\mathrm{r}}$ are 1.0 and 1.44 respectively. The velocity of light in this medium would be

In the circuits shown below, the readings of the voltmeters and the ammeters will be, 

Ionized hydrogen atoms and $\text{α}$-particles with same momenta enters perpendicular to a constant magnetic field $B$. The ratio of their radii of their paths ${r}_{H}:{r}_{\text{α}}$ will be

Two metal spheres, one of radius $\mathrm{R}$ and the other of radius $2 \mathrm{R}$ respectively have the same surface charge density $\sigma$. They are brought in contact and separated. What will be the new surface charge densities on them?

Six similar bulbs are connected as shown in the figure with a DC source of emf $E$, and zero internal resistance. The ratio of power consumption by the bulbs when $(i)$ all are glowing and $(\mathrm{ii})$ in the situation when two from section $A$ and one from section $B$ are glowing will be, 

A sphere encloses an electric dipole with charge $\pm 3 \times 10^{-6} \mathrm{C}$. What is the total electric flux across the sphere?

The reading of an ideal voltmeter in the circuit shown is 

A circuit when connected to an AC source of $12 \mathrm{~V}$ gives a current of $0.2 \mathrm{~A}$. The same circuit when connected to a DC source of $12 \mathrm{~V}$, gives a current of $0.4 \mathrm{~A}$. The circuit is