Answer Keys
Skill Sheet 20.2: Network Circuits
Part 1 answers:
R5 is zero because no current flows through this circuit.
5. ITotal = 1.5 A;
VR4 = 4.5 V
6. V5: = 5 V (ITotal = 1 A)
7. For R4 = 10 :, VA = 8 V, VB = 4 V, VAB = 8 V - 4 V = 4 V
There are no questions to answer in Part 1.
Part 2 answers:
1.
2.
3.
4.
IR2 = IR3 = 3 A; IR1 = 3 A
RTotal = 2 :
ITotal = 1 A
Answers are:
a. No, current does not
flow through R5,
because it does not
have to. The current
will go directly to R3
and R4.
b. RTotal = 9 :
c. ITotal = 2 A
d. IR3 = 1 A
e. The voltage across
Skill Sheet 20.3: Electrical Power
Parts 1 through 2:
5. Answers are:
a. 24 :
b. 600 W; 0.6 kW
6. Answers are:
a. 20 A
b. 11 :
7. Answers are:
a. 12 :
b. 1,200 W = 1.2 kW
c. 0.6 kWh
d. 18 kWh
e. $2.52
8. Your friend with the 300-watt stereo will pay more for the
energy used in an hour of play. This is because more twice as
much energy is used per second for the 300-watt stereo than
for the 150-watt stereo.
9. Since power is voltage times current, as current changes, the
power used per appliance will change. Each appliance can be
designed to carry the amount of current needed to run well.
Most electrical appliances in a dining room or living room
would run on 10 amps of current or less. However, in a
kitchen you may have an electric stove and oven that requires
40 amps of current. A special circuit with thicker wires is
installed there so that the circuit does not overheat and pose a
fire hazard.
There are no questions to answer in Parts 1 through 2.
Part 3 answers:
1.
2.
3.
4.
5.
6.
Sample problem: 270,000 joules
5,400 seconds, or 90 minutes
1,080 watts
240 volts
0.5 A
8.3 A
Part 4 answers:
1. Answers are:
a. 1.2 kW
b. 0.4 kWh
c. 12 kWh/month
d. $1.80
2. 0.63 amps
3. 960 W = 0.96 kW
4. Answers are:
a. 3 V
b. 3 :
c. 1 A
d. 3 W
Skill Sheet 21.2: Coulomb’s Law
9. The total charge equals 2.7 u 10-8 C. The square root of this
number is the value for each charge and is equal to
1.7 u 10–4 C.
10. 4.5 N; a cat weighs 49 N, this is about eleven times more
force than the force between the particles.
11. 5.5 u 10-3 C
12. distance = 6.7 m
13. distance = 0.03 m
14. q = 2.96 u 10-12 C
Part 1 answers:
There are no questions to answer in Part 1.
Part 2 answers:
1.
2.
3.
4.
5.
6.
7.
8.
It becomes 1/9 the original amount.
It becomes 1/16 the original amount.
It quadruples.
It doubles.
It quadruples.
It remains the same.
It becomes 16 times as great.
F = 9 u 109 N
16