Physics 202 MWF 10:20 Spring 1999 (Ford)

Exam II Chapts. 21--23 in Cutnell and Johnson 4e

Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.

(10 pts) 1. For the curcuit shown in the sketch, find the amplitude of the currrent through the generator when the frequency of the generator is

a) very large

Ans. ___2 A____

b) very small

Ans. ___4 A___


(18 pts) 2. A charged particle with mass m = 6.0 × 10^-14 kg and speed v = 3.0 × 10⁴ m/s enters a region of uniform magnetic field at point a, travels in a semicircular path of radius r = 0.090 m as shown, and exits the region at point b. The magnetic field has magnitude B = 0.20 T and is directed into the plane of the paper. Recall that the acceleration for uniform circular motion is a_c = v²/r. What are the magnitude and sign (positive or negative) of the charge of the particle?

Ans. q = ___1.0 × 10^-7 C____

sign ___negative____


(18 pts) 3. The triangular loop of wire shown in the sketch carries a current of I = 5.0 A in the direction shown. A uniform magnetic field is directed parallel to side ac of the triangle and has magnitude 2.0 T. The loop is free to rotate about an axis along side ab. (Recall that the area of a triangle is (1/2)(base)(height).)

a) What is the magnitude of the net torque exerted on the loop by the magnetic field?

Ans.___1.04 N·m___

b) Is the direction of the torque such as to rotate point c into or out of the plane of the paper?

Ans. ___out of plane_____


(18 pts) 4. Two long straight parallel wires are separated by 0.080 m. The wires carry currents of 6.0 A in the directions shown.

a) What is the magnitude of the net magnetic field at point a produced by the current in the two wires?

Ans. B = ___0____

b) What is the magnitude of the net magnetic field at point b produced by the current in the two wires?

Ans. B = ___4 × 10^-5 T_____________


(18 pts) 5. A rectangular loop of wire of width 0.050 m is being pulled toward the bottom of the page, as shown in the sketch, with a constant speed of v = 4.0 m/s. The loop is leaving a region in which there is a uniform magnetic field of 2.0 T directed out of the plane of the paper. The loop has resistance 0.30 .

a) What are the magnitude and direction (clockwise or counterclockwise) of the current induced in the loop?

Ans. I = ___1.33 A____

direction ___counterclockwise____

b) What are the magnitude and direction of the force F_B that the magnetic field B exerts on the loop? (Show the direction of this force on the sketch.)

Ans. F_B = ___0.133 N___

direction ___toward top of page___


(18 pts) 6. Consider the series RCL circuit shown in the sketch. The inductor has inductance L = 0.30 H and the rms voltage of the generator is 40.0 V. At the resonance frequency of f = 2.0 × 10³ Hz the power dissipated in the circuit is 25.0 W. At this frequency find the value of

a) the capacitance C of the capacitor

Ans. ___2.11 × 10^-8 F_____________

b) the resistance R of the resistor

Ans. ___64 ___

c) the rms current in the circuit

Ans. ___0.625 A___