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Example Questions
Example Question #11 : Ohm's Law
What is the voltage drop across ?
None of these
,
, and
are in parallel, so we add them by using:
We find that
,
, and
are in series. So we use:
We will then determine the total current of the circuit.
Once again, using
Where is the resistance of the resistor in question, we get
Example Question #12 : Circuits
What is the voltage drop across ?
None of these
,
, and
are in parallel, so we add them by using:
We find that
,
, and
are in series. So we use:
First, we need to find the total current of the circuit, we simply use:
Because ,
and
are in parallel,
Also, the voltage drop must be the same across all three
Using
Using algebraic subsitution we get:
Solving for
Using
Example Question #13 : Circuits
The current through is
,
has a resistance of
. Determine the voltage of the battery.
Due to the "loop rule", the voltage increase in the battery will need to be equal to the voltage drop in the resistor.
Use Ohm's law:
Combine equations:
Plug in values:
Example Question #11 : Circuit Properties
If the battery has a voltage of , and
has a resistance of
, determine the current through
.
Due to the "loop rule", the voltage increase in the battery will need to be equal to the voltage drop in the resistor.
Use Ohm's law:
Combine equations:
Plug in values:
Example Question #11 : Circuits
A battery is placed in series with five
resistors. Find the total resistance.
In series, resistance adds conventionally.
Example Question #16 : Ohm's Law
A battery is placed in series with five
resistors. Find the voltage drop across each resistor.
In series, resistance adds conventionally.
Using Ohm's law for total current:
Now use Ohm's law for an individual resistor:
Example Question #17 : Circuits
A battery is placed in series with five
resistors. Find the current.
In series, resistance adds conventionally.
Using
Example Question #21 : Circuit Properties
A single resistor is added in series to a circuit with a
battery. Determine the current.
Use Ohm's law:
Converting to
Example Question #181 : Electricity And Magnetism
In the circuit above, find the current through .
None of these
First, find the total resistance of the circuit.
and
are in parallel, so we find their equivalent resistance by using the following formula:
Next, add the series resistors together.
Use Ohm's law to find the current in the system.
The current through and
needs to add up to the total current, since they are in parallel.
Also, the voltage drop across them need to be equal, since they are in parallel.
Set up a system of equations.
Solve.
Example Question #21 : Circuits
In the circuit diagram shown below, both resistors have a resistance of ohms. If resistor
were to be removed from the circuit altogether, how would the current through
change?
The current will double
The current will halve
The current will not change
The current will increase by a factor of
The current will decrease by a factor of
The current will not change
In this question, we're shown a circuit diagram with two resistors connected in parallel. We're also told that both resistors have the same resistance. We're then asked to determine how the current through one of the resistors will change if the other one is removed.
To answer this question, we'll need to take Ohm's law into account, which states the following.
Moreover, for two resistors connected in parallel, the equivalent resistance is found by summing the inverses of the individual resistors. In the event that two resistors have the same value, as in this case, the equivalent resistance will be cut in half.
Since the equivalent resistance of the circuit is half as great as either resistor, the removal of will cause the overall resistance of the circuit to become twice as great. When the resistance becomes twice as great, and voltage does not change, the current through the circuit will become halved.
Now, it's important to realize that the current of the entire circuit becomes half as great. But remember that in the original circuit, the overall current (which was twice as great) was split between the two resistors. Thus, even though the overall current in the circuit is being cut in half, the entirety of the new current is flowing solely through . Therefore, the current flowing through this circuit does not change, even though the current for the entire circuit does.
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