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Magnetic flux passing through a coil is initially `4xx 10^-4` Wb. It reduces to 10% of its original value in t second. If the emf induced is 0.72 mV then t in second isA. `0.3`B. `0.4`C. `0.5`D. `0.6` |
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Answer» Correct Answer - C According to question, Initial flux `(phi_1) = 4 xx10^-4` Wb Final flux `(phi_2)=(4xx10^-4xx10)/100` =`4xx10^-5` Wb Emf induced is given by `e=|-(dphi)/dt| Rightarrow(dphi)/dt` Rightarrow 0.72xx10^-3=(4xx10^-4xx10^-5)/t` Rightarrow `t=(4xx10^-5xx9)/(72xx10^-5)=1/2=0.5`s |
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