Question

A parallel plate capacitor is moving with a velocity of $ 25\text{ }m{{s}^{-1}} $ through a uniform magnetic field of 1.5 T as shown in figure. If the electric field within the capacitor plates is $ 175\text{ }N{{C}^{-1}} $ and plate area is $ 25\times {{10}^{-7}}{{m}^{2}}, $ then the magnetic force experienced by positive charge plate is

• A. $ 1.45\times {{10}^{-13}}N $
• B. zero
• C. $ 8.67\times {{10}^{-15}}N $
• D. $ 3.87\times {{10}^{-15}}N $

Answer 1

Answer: (A)

Electric field in between the capacitor plates is given by $ E=\frac{q}{{{\varepsilon }_{0}}A} $ or $ q={{\varepsilon }_{0}}A\times E $ $ =8.85\times {{10}^{-12}}\times 25\times {{10}^{-7}}\times 175 $ $ =3.87\times {{10}^{-15}}C $ Magnetic force experienced by +ye plate is, $ {{F}_{m}}=qvB=1.45\times 10{{~}^{-13}}N $ in a direction out of plane of paper.