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In a cathods ray tube ,a p.d of 3000V is...

In a cathods ray tube ,a `p.d` of `3000V` is maintained betweens the deflector plates whose seperation is `2 cm`. A magnetic filed of `2.5x10^(3)` at right angle to the electric field gives no deflection of electern beam , which received an initial acceleration by a `p.d` of `10,000 V` , the `e//m` of electron is

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`V_(1)` is `p.d` between the deflector plates and `V_(2)` be the potential through which electrons are accelerated
`1/2m upsilon^(2) = V_(2)q 1/2m. V_(1)^(2)/(d^2 B^(2))=v^(2)q,q/m=V_(1)^(2)/(2d^2B^(2)V_(2))`
`(q)/(m)= (9xx10^(6))/(2xx4xx10^(-4)xx6.25xx10^(-6)xx10^(4))=1.8xx10^(11)c//kg`
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