17.4. Resistors in Series and Parallel http://www.ck12.org
FIGURE 17.13
Rparallel equivalent=RR 11 +RR^22 =(^1010 ..^00 ΩΩ)(+^66 ..^00 ΩΩ)=^60 Ω
2
16. 0 Ω=^3.^75 Ω.
The circuit is equivalent to a circuit with one 3. 75 Ωresistor.
The total current in the circuit is then:
I=RequivalentV = 312. 75.^0 ΩV= 3. 20 A.
The equivalent resistance for resistors in aseries circuitis always greater than the resistance of any one resistor in
the circuit. Conversely, the equivalent resistance for resistors in a parallel circuit is always smaller than the resistance
of any one resistor in the circuit.
In a series circuit, the current has but one pathway from the positive to the negative terminal of the battery. It’s
comparable to a traffic jam where there is no alternate route. The traffic moves very slowly. If the current is reduced,
it is a sign that the total resistance in the circuit has increased.
Conversely, if an alternate route becomes available, the traffic moves faster, since there is more than one pathway
available. If the current increases, it is a sign that the total resistance in the circuit has decreased. The latter case is
comparable to a parallel circuit where there are multiple branches through which the current can travel.
http://demonstrations.wolfram.com/ResistorsInParallel/
http://www.youtube.com/watch?v=Dx3njY0vUZM
Check Your Understanding
- What are the voltage drops across resistorsR 1 andR 2 inFigure17.12?
Answer:The resistances are in series. The total voltage across the entire circuit is 12 volts. The sum of voltage
dropV 1 and of voltage dropV 2 must equal 12 volts. The current through each resistor is the same (see above). The
voltage drop acrossR 1 isV 1 =IR 1. The voltage drop acrossR 2 isV 2 =IR 2.