Multiple-Choice Homework Problem 22.3 An electronics company wants you to design

Question

Multiple-Choice Homework Problem 22.3 An electronics company wants you to design an inductor using a prototype metallic alloy wire which can handle high currents. You decide to build a solenoid that is 7cm long with a radius of 2cm. You are able to fit 650 turns of the wire on the solenoid. Calculate the inductance of the solenoid approximating it as an infinite solenoid.

(a) L = 1.5 × 105H.

(b) L = 6.7 × 104H.

(c) L = 9.5 × 103H.

(d) L = 3.0 × 102H.

(e) L = 4.8 × 101H.

Multiple-Choice Homework Problem 22.7 You have grown tired of the small displacement currents we have

been able to produce. To produce a decent current, you take a circular parallel-plate capacitor with radius 15cm

and fill it with TNT as the dielectric. You then charge the capactor with a high voltage power supply. When

you reach breakdown voltage, the capacitor blows up and the plates move apart at Mach 1, the speed of sound

(v = 340 m ). The plate separation as a function of time is given by l(t) = d0 + vt where d0 = 1mm, the capacitor s

spacing before the explosion. The spark occurs at a voltage V0 = 10,000V. If the power supply briefly stays connected, the electric field between the plates as a function of time as they initially blow apart is

E= V0 d0 + vt

where the plates start to move apart at t = 0. Compute displacement current through a surface of radius 15cm at t = 0.

(a) 0.033A (b) 0.45A (c) 2.1A (d) 170A (e) Toby

Explanation / Answer

1) Inductance = L = uo*N^2*A/L

L = (4pi*10^-7*650^2*pi*0.02^2)/0.07 = 9.5 × 10^3 H. (Option C is correct)

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