I can't figure out how they got the answers they did on these questions.

Can anyone out there help?

For 81 I get (c) for an anwer not (d) Maybe something to do with
it being a parallel circuit instead of a series. Didn't know they had
different
formulas.

I get (c) for 86. Same story.

I get 300 - j318 for (88)

Can't figure out the other two also.




81] What is the impedance of a network composed of a
100-picofarad capacitor in parallel with a 4000-ohm resistor, at
500 kHz? (Specify your answer in polar coordinates.)

a} 2490 ohms, /51.5 degrees.

b} 4000 ohms, /38.5 degrees.

c} 5112 ohms, / -38.5 degrees.

d} 2490 ohms, /-51.5 degrees.@@




86] What is the impedance of a network composed of a
400-ohm-reactance inductor in parallel with a 300-ohm resistor?
(Specify your answer in polar coordinates.)

a} 240 ohms, / 36.9 degrees.@@

b} 240 ohms, / -36.9 degrees.

c} 500 ohms, / 53.1 degrees.

d} 500 ohms, / -53.1 degrees.



88] What is the impedance of a network composed of a
0.01-microfarad capacitor in parallel with a 300-ohm resistor, at
50 kHz? (Specify your answer in rectangular coordinates.)

a} 150 - j159.

b} 150 + j159.

c} 159 + j150.

d} 159 - j150.@@







111] A 6 volt battery with 1.2 ohms internal resistance is
connected across two 3 watt bulbs. What is the current flow?

a} .57 amps.

b} .83 amps.@@

c} 1.0 amps.

d} 6.0 amps.



129] How many capacitors of 400 volts and 2.0 microfarads each
would be necessary to obtain a combination rated at 1600 volts
and 1.5 microfarads?

a} 10.

b} 12.@@

c} 14.

d} 16.