Induction and Alternating Current with teacher's notes

SECTION 22-2
PRACTICE GUIDE 22C
Solving for:
V PE Sample, 1, 4, 5a,
6; Ch. Rvw.
25–28
PW Sample, 4–6
PB Sample, 1, 4,
5–6, 9
I PE Sample, 1–2, 3a,
4, 5b; Ch. Rvw.
26–28
PW Sample, 1–4,
5, 7
PB Sample, 1–4,
5, 7, 8–10
R PE 3b
PW 3, 5
PB 3, 5
P PE Ch. Rvw. 27
PW Sample, 1
PB 8–10
ANSWERS TO
Practice 22C
rms currents and potential
differences
1. 4.8 A; 6.8 A, 170 V
2. 7.8 A
3. a. 7.42 A
b. 14.8 Ω
4. 1.44 A; 2.04 A, 21.2 V
5. a. 1.10 × 10 2 V
b. 2.1 A
6. 319 V
810
810
3. CALCULATE
4. EVALUATE
PRACTICE 22C
Chapter 22
Substitute the values into the equation(s) and solve:
∆Vrms = (0.707)(205 V) = 145 V
145
V
Irms = ⎯⎯ = 1.26 A
115
Ω
Imax = ⎯ 1.
26
A
⎯ = 1.78 A
0.
707
∆Vrms = 145 V
Irms = 1.26 A
Imax = 1.78 A
The rms values for potential difference and current are a little more than
two-thirds the maximum values, as expected.
rms currents and potential differences
CALCULATOR SOLUTION
Because the minimum number of
significant figures for the data is three,
the calculator solution for the rms
potential difference, 144.935, should
be rounded to three digits.
1. What is the rms current in a light bulb that has a resistance of 25 Ω and
an rms potential difference of 120 V? What are the maximum values for
current and potential difference?
2. The current in an ac circuit is measured with an ammeter. The meter
gives a reading of 5.5 A. Calculate the maximum ac current.
3. A toaster is plugged into a source of alternating potential difference with
an rms value of 110 V. The heating element is designed to convey a current
with a maximum value of 10.5 A. Find the following:
a. the rms current in the heating element
b. the resistance of the heating element
4. An audio amplifier provides an alternating rms potential difference of
15.0 V. A loudspeaker connected to the amplifier has a resistance of
10.4 Ω. What is the rms current in the speaker? What are the maximum
values of the current and the potential difference?
5. An ac generator has a maximum potential difference output of 155 V.
a. Find the rms potential difference output.
b. Find the rms current in the circuit when the generator is connected to
a 53 Ω resistor.
6. The largest potential difference that can be placed across a certain capacitor
at any instant is 451 V. What is the largest rms potential difference
that can be placed across the capacitor without damaging it?
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