Question: Q. 5. Describe the concept used for the selection of velocity of a charged particle. Explain the principle of the device with the help of a diagram where the same concept is used. What is the resonating condition for the said device ? $\square$ [CBSE SQP, 2016]
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Solution:
Ans. $\frac{E}{B}=v$ when $E, v$ and $B$ are perpendicular to each other. 1 Cyclotron, $E$ is perpendicular to $B$ is perpendicular to $v$, In presence of $E$ parabolic path and in presence of $B$ circular path. $T$ and $v$ are independent of radius of the path.
1
When frequency of oscillator is same as frequency of cyclotron then resonance occurs.
[CBSE Marking Scheme, 2016]
Detailed Answer :
(i) Velocity selection : Try yourself, Similar to Q. 1, Short Answer Type Questions-I.
(ii) From the expression $q E=q v B$, velocity selects those particles with speed $v$ that pass undeflected through mutually perpendicular electric and magnetic fields where magnetic force exerted on particles moving at speeds more than this will be stronger than electric force making the particles to deflect upward while speed less than this gets deflected downward.
The resonating conditions in cyclotron occurs when frequency of applied voltage is kept exactly same as frequency of revolution of proton, then every time the proton reaches the gap between the two dees and makes the electric field reversed thereby receiving a push and resulting in very high energy.
