NEET Class neet Answered

Q no 2

Asked by manasvijha | 25 Mar, 2019, 07:40: AM

Expert Answer

when a proton is released from rest, intitially it is accelerated twowards west direction due to electric field which is acting westwards

begin mathsize 12px style stack F subscript e with rightwards arrow on top space equals space e space E with rightwards arrow on top space equals space m left parenthesis stack a subscript 0 with rightwards arrow on top space right parenthesis space space space space o r space space open vertical bar E with rightwards arrow on top close vertical bar space equals space fraction numerator space m space a subscript 0 over denominator e end fraction space space end style

( in west direction ) ..............................(1)

when the proton is projected in North direction with velocity v₀ , proton is subjected to electric field and magnetic field.

Proton is moving towards west with acceleration 3a₀ . Since

begin mathsize 12px style v with rightwards arrow on top space cross times B with rightwards arrow on top space end style

force is acting in west direction and its velocity is towards north ,

magnetic field is acting downward direction ( see figure )

since it is known that electric field gives an acceleration a_o , additional acceleration 2a_ois given by magnetic field

begin mathsize 12px style stack F subscript m with rightwards arrow on top space equals e left parenthesis space v with rightwards arrow on top space cross times B with rightwards arrow on top right parenthesis space equals space m open parentheses 2 stack a subscript o with rightwards arrow on top close parentheses space space space space space o r space space space space space space space open vertical bar B with rightwards arrow on top close vertical bar space equals space fraction numerator 2 m space a subscript 0 over denominator e space v subscript o end fraction end style

( downward direction )

Hence in the list of options given in the answer, (b) is the correct one

Answered by Thiyagarajan K | 25 Mar, 2019, 02:16: PM

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