1. A 120-V rms voltage at 1000 Hz is applied to a 2.00-mH inductor, a 4.00-uF ca

Question

1. A 120-V rms voltage at 1000 Hz is applied to a 2.00-mH inductor, a 4.00-uF capacitor and a resistor. If the rms value of the current in this circuit is 0.400 A, what is the value of the resistor?

A) 95.1 ? B) 423 ? C) 240 ? D) 120 ? E) 299 ?

2. In the radiation field from an antenna, the electric and magnetic fields are
A) parallel to one another.
B) never in any geometric arrangement with respect to one another.
C) anti-parallel to one another.
D) anti-perpendicular to one another.
E) perpendicular to one another.

3. Generators that were used in the past to supply electricity in automobiles have been replaced
by
A) armatures.
B) dynamos.
C) batteries.
D) alternators.
E) commutators.

4. In a pure resistive circuit, the phase angle between current and voltage is
A) ? radians.
B) 0.
C) ?/2 radians.
D) -?/2 radians.
E) 3?/4 radians.

5. A solenoid of length 5.0 cm has a cross sectional area of 1.0 cm2 and has 300 uniformly spaced
turns. The solenoid is wrapped in 180 turns of insulated wire resulting in a mutual inductance
of
A) 110 H.
B) 1.4

Explanation / Answer

. A 120-V rms voltage at 1000 Hz is applied to a 2.00-mH inductor, a 4.00-uF capacitor and a resistor. If the rms value of the current in this circuit is 0.400 A, what is the value of the resistor?

E) 299 ?-------ANSWER

XL = (6.28)*(1,000)*(.002) = 12.56 Ohm
XC = 1/ [(6.28)*(1,000)*(.000004)] = 39.81 Ohm
net reactance = (12.56 - 39.81)Ohm = -27.25 Ohm (negative sign indicates that the net reactance is capacitive)
Z = 120V/.4A = 300 Ohm
R = (300)*[cos(arc sin -27.25/300)] = 298.76 Ohms

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