Electrostatics MCQs – Test 1 6

6 thoughts on “Electrostatics MCQs – Test 1”

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  SMRITHI May 27, 2017 at 10:16 am

  It was a very useful experience .I learnt a lot.
  Thankyou very much!!!

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  amisha July 1, 2017 at 8:53 am

  Give the explaination of question 5

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    Ambuj tiwari February 18, 2018 at 10:57 pm

    In q.5 ,Tcos15=mg and Tsin15=F. And when it is immersed in liquid then tan15=F÷K/mg(1-density of liquid÷d.of substance). And tan15 is constant and it is found to divide upper two equation. And when it goes in liquid then Force is changes into F÷K. Where k is dielectric constant which is ask and mg is also changes so easily it is found

  • Reply ↓

    Chirag.K April 10, 2019 at 3:20 pm

    Hi AMISHA,
    As mg’ = mg – Upthrust

    = mg – V*sigma*g (since upthrust = v*sigma*g)

    mg’ = mg[1- sigma/rho]

    T cos Theta=mg –(i)

    T sin Theta=F –(ii)

    Therefore from equation (i) and (ii)

    tan Theta = F/mg —-(iii)

    Now for the equilibrium of balls

    tan Theta’ = F’/mg’ = F/Kmg[1-(rho/sigma)]

    = f/(kmg(1-{sigma/rho }) –(iv)

    According to question Theta’=Theta

    from equation (iv) & (iii)

    K=1/(1-(sigma /rho))

    =rho/(rho -sigma ) =1.6/(1.6-0.8)=2

    K=2

    Hope this helps! 🙂

    Chirag K

  • Reply ↓

    king April 10, 2019 at 3:22 pm

    Coulombic force –

    F\propto Q_{1}Q_{2}=F\propto \frac{Q_{1}Q_{2}}{r^{2}}=F=\frac{KQ_{1}Q_{2}}{r^{2}}

    – wherein

    K – proportionality Constant

    Q1 and Q2 are two Point charge

    T\cos \Theta=mg –(i)

    T\sin \Theta=F_{e} –(ii)

    \therefore from equation (i) & (ii)

    Tan \Theta=\frac{F_{e}}{mg}—(iii)

    if ball is suspended in liquid g’=g[1-\frac{\sigma }{\rho }]

    Tan \Theta’=\frac{F’_{e}}{mg’}

    =\frac{f}{kmg(1-\frac{\sigma}{\rho })} –(iv)

    According to question \Theta’=\Theta

    from equation (iv) & (iii)

    K=\frac{1}{1-\frac{\sigma }{\rho }}

    =\frac{\rho }{(\rho -\sigma )} =\frac{1.6}{(1.6-0.8)}=2
    K=2

  • Reply ↓

    Arghadeep Basu June 14, 2020 at 12:53 pm

    As we have studies dielectric in capacitors there’s the concept of dielectric in charges also that dielectric constant (K)= density of material / (density of material – density in medium)