An electron moves in a circular orbit with a uniform speed $v$. It produces a magnetic field $B$ at the centre of the circle. The radius of the circle is proportional to
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A $50\,\Omega $ resistance is connected to a battery of $5\,V$. A galvanometer of resistance $100\, \Omega $ is to be used as an ammeter to measure current through the resistance, for this a resistance $r_s$ is connected to the galvanometer. Which of the following connections should be employed if the measured current is within $1\% $ of the current without the ammeter in the circuit ?
A long solenoid of radius $1\,mm$ has $100 $turns per $mm$. If $1\,A$ current flows in the solenoid, the magnetic field strength at the centre of the solenoid is:
A moving coil galvanometer has $48$ $turns$ and area of coil is $4 \times {10^{ - 2}}\,{m^2}.$ If the magnetic field is $0.2\, T$, then to increase the current sensitivity by $25\%$ without changing area $(A)$ and field $(B)$ the number of turns should become
Assertion : If the current in a solenoid is reversed in direction while keeping the same magnitude, the magnetic field energy stored in the solenoid decreases.
Reason : Magnetic field energy density is proportional to square of current.
If two protons are moving with speed $v=4.5 \times 10^{5} \,m / s$ parallel to each other then the ratio of electrostatic and magnetic force between them
An ammeter gives full scale deflection when current of $1.0\, A$ is passed in it. To convert it into $10\, A$ range ammeter, the ratio of its resistance and the shunt resistance will be
$A$ microammeter has a resistance of $100\,\Omega$ and $a$ full scale range of $50\,\mu$ $A$. It can be used as a voltmeter or a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combination $(s)$.
Statement $-1$ : Path of the charge particle may be straight line in uniform magnetic field. Statement $-2$ : Path of the charge particle is decided by the angle between its velocity and the magnetic force working on it