Download Electric Circuits Review

Electric Circuits Review
Chapters 17 & 18
Electrical resistance in a wire
depends on the wire’s
Resistivity
2. Length
3. Cross sectional area
4. All of the above
1.
When two light bulbs are
connected in series
The same amount of current flows through
each light bulb.
2. The current through each light bulb is
proportional to the resistivity of the bulb.
3. The light bulbs will not work unless there is
a fuse in the circuit.
4. There are at least two branches of the
circuit.
1.
When one light bulb burns out in a series
circuit containing several light bulbs …
a. The other light bulbs burn more brightly
b. Nothing changes in the rest of the
circuit
c. None of the other bulbs will light up
When resistors are put in series, their
overall resistance is
a. Larger than that of any individual resistor
b. The same as the resistance of one of the
resistors
c. Smaller than the resistance of any of the
resistors
When resistors are put in parallel, their
overall resistance is
a. Larger than that of any individual resistor
b. The same as the resistance of one of the
resistors
c. Smaller than the resistance of any of the
resistors
A wire 5.0 m long and 3.0 mm in diameter has a resistance
of 100. W. A 15 V potential difference is applied across
the wire. What is the current in the wire?
V  IR
V 15
I 
 0.15A
R 100

Two appliances operate at the same voltage. Appliance A
has a higher power rating then appliance B. How does the
resistance on A compare with that of B
1.
2.
3.
A’s resistance is larger than B’s.
A’s resistance is smaller than B’s
A’s resistance is the same as B’s.
V
P
R
2
What is the resistance of a 100. W light
bulb if it is plugged into a 120. V outlet?
V
P
R
2
120
100 
R
R  144W
2
Three resistors with resistance of 6 W, 12 W,
and 24 W are connected in series. What is the
total resistance of the circuit?
Rtotal  612 24  42W
Three resistors with resistance of 6.0 W, 12 W, and 24
W are connected in series with a 12V battery. What is
the current through the 12 W resistor?
V  IR
12  42I
I  0.29A
The current is the
same through all
of them so the total
resistance must
be used.
What is the total resistance of this
partial circuit?
6W
6W
12 W
6W
6W
12 W
Rtop  612 18W

1
1 1 4
  
Rtotal 18 6 18
18
Rtotal   4.5W
4
What is the current through each of the resistors in
the following circuit?
(Rtotal = 4.5 W)
6W
6W
12 V
12 W
6W
12 V / 6 W = 2 A
6W
12 V / 18 W = 0.67 A
12 W
12 V / 18 W = 0.67 A
What is the current in the 10-W resistor?
1
Rparallel
1 1 1 6 10 15
   
10 6 4
60
60
Rparallel 
 1.94W
31
Rtotal  1.94  2  3.94W
V
12

I total 

 3.05A
Rtotal 3.94
Vparallel  IRparallel
Vparallel  (3.05)(1.94)
Vparallel  5.91V
Vparallel
I10W 
R10W
I10W
5.91

 0.59A
10
Which two resistors are in parallel
with each other?
R2 and R3
Teams, place your bets
How much power is being dissipated by
one of the 10 W resistors?
P = IV = V2/R = I2R
I total 
V
12
  2A
Rtotal 6
Vparallel  IRparallel
1
Rparallel
1 1 1  5
   
10 10 20 20
Rparallel  4W
Rtotal  2  4  6W

Vparallel  (2)(4)  8V
Vparallel 8 2
P10W 
  6.4W
R10W 10
2