4. (5%) The parallel-plate capacitor is shown in following figure. The electric field is(A)(B)(C)(D)

1. (5%) A cylindrical capacitor consists of an inner conductor of radius a, and an outer conductor whose inner radius is b. The space between the conductors is filled with a dielectric of permittivity ε. The length of the capacitor is L. The capacitance of this this capacitor is (A) C=2πεL/ln(b/a) (B) C=2πεL/In(a/b)(C)C=2πεL/In(ab) (D) none of the mentioned