A straight rod of mass $m$ and length $L$ is suspended from the identical spring as shown in the figure. The spring stretched by a distance of $x_0$ due to the weight of the wire. The circuit has total resistance $R\Omega$ . When the magnetic field perpendicular to the plane of the paper is switched on, springs are observed to extend further by the same distance. The magnetic field strength is
Diffcult
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An infinitely long conductor $PQR$ is bent to form a right angle as shown. A current $I$ flows through $PQR$ The magnetic field due to this current at the point $M $ is $H_1$. Now another infinitely long straight conductor $QS$ is connected at $Q$ so that the current is $I/2$ in $QR$ as well as in $QS$, The current in $PQ$ remaining unchanged. The magnetic field at $M$ is now ${H_{2.}}$The ratio ${H_1}/{H_2}$ is given by
A galvanometer has a resistance of $20\,\Omega$ and reads full-scale when $0.2\, V$ is applied across it. To convert it into a $10\, A$ ammeter, the galvanometer coil should have a
One of the two small circular coils, (none of them having any self- inductance) is suspended with a $V-$ shaped copper wire, with plane horizontal. The other coil is placed just below the first one with plane horizontal. Both the coils are connected in series with a $dc$ supply. The coils are found to attract each other with a force. Which one of the following statements is incorrect ?
An electron enters a chamber in which a uniform magnetic field is present as shown below. An electric field of appropriate magnitude is also applied, so that the electron travels undeviated without any change in its speed through the chamber. We are ignoring gravity. Then, the direction of the electric field is
A coil of $12$ turns made by a constant length current carrying wire. If number of turns makes $3$ then change in magnetic field produced at its centre
Consider three quantities $x = E/B,$ $y =\sqrt {1/{\mu _0}{\varepsilon _0}} $ and $z = l$ . Here, $l$ is the length of a wire, $C$ is a $CR$ capacitance and $R$ is a resistance. All other symbols have standard meanings.
A single circular loop of radius $1.00\, m$ carries a current of $10.0\, mA$. It is placed in $a$ uniform magnetic field of magnitude $0.500\, T$ that is directed parallel to the plane of the loop as suggested in the figure. The magnitude of the torque exerted on the loop by the magnetic field is.
A long solenoid is producing magnetic field on its axis is $B$. If it is cuts into four equal parts and for same current, half number of turns wound on any on piece than value of magnetic field on it axis becomes
Two moving coil meters $M_1$ and $M_2$ having the following particulars :-
$R_1 = 10\,\Omega , N_1 = 30, A_1 = 3.6\times10^{-3}\, m^2, B_1 = 0.25\, T$
$R_2 = 14\,\Omega , N_2 = 42, A_2 = 1.8\times10^{-3}\, m^2, B_2 = 0.50\, T$
(The spring constants are identical for the two meters). Determine the ratio of voltage sensitivity of $M_2$ and $M_1$