Magnetic Effects Of Current Question 325
Question: An electron of mass m and charge q is travelling with a speed v along a circular path of radius r at right angles to a uniform of magnetic field B. If speed of the electron is doubled and the magnetic field is halved, then resulting path would have a radius of [Kerala PMT 2004; KCET 2000, 05]
Options:
A) $ \frac{r}{4} $
B) $ \frac{r}{2} $
C) $ 2r $
D) $ 4r $
Show Answer
Answer:
Correct Answer: D
Solution:
$ r=\frac{mv}{qB}\Rightarrow \frac{r_{1}}{r_{2}}=\frac{v_{1}}{v_{2}}\times \frac{B_{2}}{B_{1}}\Rightarrow \frac{r_{1}}{r_{2}}=\frac{1}{2}\times \frac{1}{2}=\frac{1}{4} $ $ r_{2}=4r_{1} $
BETA
