1.

Two opposite and equal chrages `4 xx 10^(-8)` coulomb when placed `2 xx 10^(-2) cm` away, from a dipole. If dipole is placed in an ecternal electric field `4 xx 10^(8)` newton//coulomb, the value of maximum torque and the work done in rotating it through `180^(@)` will beA. `64 xx 10^(-4) Nm` and `64 xx 10^(-4) J`B. `32 xx 10^(-4) Nm` and `32 xx 10^(-4) J`C. `64 xx 10^(-4) Nm` and `32 xx 10^(-4) J`D. `32 xx 10^(-4) Nm` and `64 xx 10^(-4) J`

Answer» Correct Answer - D
Dipole moment `p = 4 xx 10^(-8) xx 2 xx 10^(-4) = 8 xx 10^(-12) m`
Maximum torque `= pE = 8 xx 10^(-12) x 4 xx 10^(8)`
`= 32 xx 10^(-4) Nm`
Work done in rotating through `180^(@) = 2pE`
`= 2 xx 32 xx 10^(-4) = 64 xx 10^(-4) J`


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