All AP Physics 1 Resources
Example Questions
Example Question #1 : Series And Parallel
If we have 3 resistors in a series, with resistor 1 having a resistance of , resistor 2 having a resistance of , and resistor 3 having a resistance of , what is the equivalent resistance of the series?
The total resistance of resistors in a series is the sum of their individual resistances. In this case,
Example Question #1 : Series And Parallel
You are presented with three resistors, each measure . What is the difference between the total resistance of the resistors combined in series, and the total resistance of the resistors combined in parallel?
Resistors in series:
Resistors in parallel:
Example Question #1 : Series And Parallel
What is the total resistance of three resistors, , , and , in parallel?
The equation for equivalent resistance for multiple resistors in parallel is:
Plug in known values and solve.
Notice that for resistors in parallel, the total resistance is never greater than the resistance of the smallest element.
Example Question #1 : Series And Parallel
A circuit is created using a battery and 3 identical resistors, as shown in the figure. Each of the resistors has a resistance of . If resistor is removed from the circuit, what will be the effect on the current through resistor ?
The current through will decrease
The current through will increase by a factor of two
The current through will remain the same
The current through will increase by a factor of four
Cannot be determined without knowing the resistivity of the wire
The current through will decrease
Since the resistors and form a parallel network, removing from the circuit increases the resistance of that part of the circuit. Because the new circuit is the series combination of and , the increased resistance leads to lower current in each of these resistors.
Example Question #1 : Series And Parallel
Determine the total charge stored by a circuit with 2 identical parallel-plate capacitors in parallel with area , and a distance of between the parallel plates. Assume the space between the parallel plates is a vacuum. The circuit shows a voltage difference of 10V.
To determine total charge stored, we need to add up the capacitance of each capacitor(because they are capacitors in parallel) and multiply by the voltage difference. Recall that for capacitors,
For parallel plate capacitors:
Here, , which is the permittivity of empty space, is the dielectric constant, which is since there is only vacuum present, , which is the area of the parallel plates, and , which is the distant between the plates.
Plug in known values to solve for capacitance.
Each of the two capacitors has capacitance
Since the capacitors are in parallel, the total capacitance is the sum of each individual capacitance. The total capacitance in the circuit is given by:
Plug this value into our first equation and solve for the total charge stored.
, where is the total charge stored in the capacitor. Since
Example Question #1 : Series And Parallel
What is the total current flowing through a system with 2 resistors in parallel with resistances of and , and a battery with voltage difference of 10V?
First we need to determine the overall resistance of the circuit before we know how much current is flowing through. Since the resistors are in parallel, their resistances will add reciprocally:
where is the total resistance of the circuit.
Now that we've solved for , we know that the current flowing through the circuit can be found using Ohm's law:
Example Question #11 : Series And Parallel
Consider two circuits: one contains two resistors wired in series, each with a resistance of , while the other contains two resistors wired in parallel, one with a resistance of and the other with an unknown resistance. The circuits are completely independent, each having its own battery, and each drawing a current of . What must the resistance of the unknown resistor be for the two circuits to have the same total resistance?
The total resistance of a circuit in series can be described by the equation:
The series circuit in ths problem therefore has a resistance of:
The resistance of a circuit wired in parallel has a total resistance of:
We are assuming that the two circuits have the same total resistance, so to find the resistance of the unknown resistor, we set up the following equation:
This, when solved, gives us a resitance of 200 ohms for our unknown element.
Example Question #1331 : Ap Physics 1
Three batteries are connected in series. What is their equivalent voltage?
The equivalent voltage of batteries connected in series is the sum of the voltage of each battery, or
In our problem,
Example Question #1332 : Ap Physics 1
Three batteries are connected in parallel. What is their equivalent voltage?
The equivalent voltage of batteries connected in parallel is equal to the voltage of 1 battery.
In this problem,
Note: Connecting batteries in parallel increases the capacity of the battery.
Example Question #12 : Series And Parallel
Four resistors, , , and , are arranged as follows. What is the equivalent resistance of this setup?
To find the equivalent resistance of this system, we must first find the equivalent resistance of the resistors in parallel, then evaluate the resistors in parallel.
The parallel resistor equivalence is given by the following equation,
In our problem,
The parallel resistors can now be treated as one resistor with the resistance . To find the total resistance, we add the resistances of , and .
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