Consider a thin metallic sheet perpendicular to the plane of the paper moving with speed $'v'$ in a uniform magnetic field $B$ going into the plane of the paper (See figure). If charge densities ${\sigma _1}$ and ${\sigma _2}$ are induced on the left and right surfaces, respectively, of the sheet then (ignore fringe effects)
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A beam of electrons passes undeflected through mutually perpendicular electric and magnetic fields. It the electric field is switched off, and the same magnetic field is maintained, the electrons move
A galvanometer whose resistance is $120\,\Omega $ gives full scale deflection with a current of $0.05\, A$ so that it can read a maximum current of $10\, A$. A shunt resistance is added in parallel with it. The resistance of the ammeter so formed is .............. $\Omega $
A straight wire $AB$ of mass $40\,g$ and length $50\,cm$ is suspended by a pair of flexible leads in uniform magnetic field of magnitude $0.40\,T$ as shown in the figure. The magnitude of the current required in the wire to remove the tension in the supporting leads is ...........$A$. (Take $g=10\,ms ^{-2}$ ).
Which one of the following modifications may ncrease the sensitivity of moving coil galvanometer?
$1^{st}$ Way : By using spring of smaller torsion constant.
$2^{nd}$ Way : By using a smaller coil
$3^{rd}$ Way : By using a stronger magnet
$4^{th}$ Way : By using a coil having fewer number of turns.
The electric current in a circular coil of four turns produces a magnetic induction $32\,T$ at its centre. The coil is unwound and is rewound into a circular coil of single turn, the magnetic induction at the centre of the coil by the same current will be $..........\,T$
A square loop of side $a$ hangs from an insulating hanger of spring balance. The magnetic field of strength $B$ occurs only at the lower edge. It carries a current $I$. Find the change in the reading of the spring balance if the direction of current is reversed
A small coil of $N$ $turns$ has an effective area $A$ and carries a current $I$. It is suspended in a horizontal magnetic field $\overrightarrow B $ such that its plane is perpendicular to $\overrightarrow B $. The work done in rotating it by $180^\circ $ about the vertical axis is
Heart-lung machines and artifical kidney machines employ blood pumps. A mechanical pump can mangle blood cells.Figure represents an electromagnetic pump. The blood is confined to an electrically insulating tube, represented as a rectangle of width $\omega$ and height $h.$ Two electrodes fit into the top and the bottom of the tube. The potential difference between them establishes an electric current through the blood, with current density $J$ over a section of length $L.$ A perpendicular magnetic field exists in the same region. The section of liquid in the magnetic field experiences a pressure increase given by :-