Electron of mass m and charge q is travelling with a speed along a circular path of radius r at righ

English

Gujarati

Hindi

4.Moving Charges and Magnetism

medium

Electron of mass $m$ and charge $q$ is travelling with a speed along a circular path of radius $r$ at right angles to a uniform magnetic field of intensity $B$. If the speed of the electron is doubled and the magnetic field is halved the resulting path would have a radius

A

$2\,r$

B

$4\,r$

C

$\frac {r}{4}$

D

$\frac {r}{2}$

(AIIMS-2009)

Solution

Radius of path is given by $r=\frac{m v}{B q}$

Here, $\mathrm{m}$ and $\mathrm{q}$ remain unchanged

So, $\frac{r_{1}}{r_{2}}=\frac{v_{1}}{v_{2}} \cdot \frac{B_{2}}{B_{1}}=\frac{v}{2 v} \cdot \frac{B / 2}{B}=\frac{1}{4}$

$\Rightarrow r_{2}=4 r$

Standard 12

Physics

Share

Similar Questions

In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential $V$ and then made to describe semicircular paths of radius $R$ using a magnetic field $B$. If $V$ and $B$ are kept constant, the ratio $\left( {\frac{{{\text{charge on the ion}}}}{{{\text{mass of the ion}}}}} \right)$ will be proportional to

hard

(AIPMT-2007)

For a positively charged particle moving in a $x-y$ plane initially along the $x$-axis, there is a sudden change in its path due to the presence of electric and/or magnetic fields beyond $P$. The curved path is shown in the $x-y$ plane and is found to be non-circular. Which one of the following combinations is possible

hard

(IIT-2003)

The time period of a charged particle undergoing a circular motion in a uniform magnetic field is independent of its

easy

(AIEEE-2002)

A homogeneous electric field $E$ and a uniform magnetic field $\mathop B\limits^ \to $ are pointing in the same direction. A proton is projected with its velocity parallel to $\mathop E\limits^ \to $. It will

easy

If an electron enters a magnetic field with its velocity pointing in the same direction as the magnetic field, then

easy