Chapter 63: The Detection and Measurement of Electric Charges
The part of the rod in contact with the cloth becomes charged when ebonite is rubbed with cloth.
The name static refers to the charge being local for some time.
Among others, rubber, plastic and glass are called insulator.
There are two reasons a metal rod cannot be charged statically.
Electric charges can flow through metals as conductors.
Your body is a conductor and any charges placed in the metal rod are conducted through you.
The effect is called grounding.
The silver-coated pith balls mentioned in the first section of this chapter can become statically charged because they are suspended by thread.
They can be used to detect the presence and sign of an electric charge, but they are not very helpful in obtaining a qualitative measurement of the magnitude of charge they possess.
The electroscope is used for qualitative measurement.
There are two "leaves" made of gold foil.
The leaves are vertical when the scope is not charged.
The leaves change color when a negatively charged rod is near.
If we recall the hypothesis that only negative charges move in the air, we can understand that the electrons are repelled down to the leaves through the conducting stem.
As long as the rod is not touching the knob, it will become positively charged.
The leaves will collapse if you take the rod away.
The electrons are transferred to the knob, stem, and leaves.
The whole scope becomes negatively charged.
The extent to which the leaves are spread apart is an indication of how much charge is present.
The leaves will collapse if you touch the electroscope.
The electroscope can be charged with electricity.
The repelled electrons will be forced out into your body if you touch the electroscope with your finger.
The electroscope will have a positive charge if you remove your finger.
We can state that electric charges obey a law.
We always maintain a balanced accounting when we transfer charge.
We have metal spheres.
Both sphere A and sphere B have positive elementary charges.
The two spheres are near each other.
Since they repel each other, excess charges are spread out as far apart as possible.
If the net charge on both objects is positive, the electrons will move even if the charges are allowed to flow.
If the two spheres are equal in size, each will have a +3 charge if enough electrons move from the +2 sphere to the +3 sphere.
If one object is larger than the other, the larger object will have more of the net excess charge spread out around the outer surfaces of the combined object.
We can conclude from the first two sections of the chapter that charges repel each other, and unlike charges attract.
The force between two charged objects can move through space.
The force of gravity is similar to the force of this property.
The charge is measured in coulombs.
The inverse square law is very similar to the law of gravitation.
The force of gravity can be mitigated by the electrostatic force.
There can be repulsion as well as attraction.
The nature of the force was studied by a French scientist.
The force between q 1 and q 2 was caused by a mutual force along a line connecting the charges that varied directly as the product of the charges and the square of the distance between them.
The inverse square law of Coulomb's law is similar to the law of gravity.
M 2 /C 2 is 9 x 10.
Coulomb's law is similar to the law of universal gravitation.
The two point sources are connected by a radial vector.
Coulomb's law only applies to one pair of point sources or sources that can be treated as point sources, such as charged spheres.
The net force on one charge is the sum of all the other forces.
Superposition is an aspect of force addition.
The force is attractive because of the negative sign.
F 1 is the electric force of 175 mC charge.
It will go straight up.
F 2 is the electrical force of the charge.
It will go straight to the right.
Negative charges will flow from a higher concentration to a lower one if two points are connected with a conductor.
This part of charge flow is very similar to the flow of water in a pipe.
The amount of charge passing a point every second is referred to as electric current.
The units of measurement are coulombs.
The battery supplies the potential difference needed to maintain a continuous flow of charge.
Physicists thought that the electric force pushed the electric fluid through the conductor.
We know that an emf is not a force but a potential difference.
A battery uses acids and bases on different metals to free electrons and maintain a potential difference.
Two terminals are created in the process.
A complete circle of wire is produced when a conducting wire is looped around the other end.
The battery uses chemical reactions to raise electrons from the positive side to the negative side.
The electrons can transform their electric potential energy into other forms of energy.
Our modern world has become familiar with the electricity of this work.
A simple electric circuit is shown in the diagram.
The direction of the conventional current is from the positive terminal.
To maintain a universal acceptance of concepts and ideas, schematic representations for electrical devices were developed and accepted by physicists and electricians worldwide.
When drawing or diagramming an electric circuit, it's important that you understand the basics of the schematic.
Some of the most frequently encountered electrical devices are presented in the schematic.
The simple circuit shown in can now be diagrammed.
The charge would not flow unless the switch was closed.
An open switch stops the flow.
We have not yet discussed three of the schematics.
The function of a Resistor is to use up voltage.
In the next section, we will look at the resistors in more detail.
An ammeter is used to measure the current.
You can find the water meter in your house or apartment building by looking at the flow line.
The meter has to measure the flow of water through a point.
An electric circuit has an ammeter within it.
The series connection maintains the singular nature of the circuit.
You can imagine cutting a wire and hooking up the bare leads to the ammeter.
Ammeters have low resistance.
A voltmeter is a device that measures the potential difference between two points.
The voltmeter can't be placed within the circuit since it will be connected to only one point.
A second circuit through which only a small amount of current flows to operate the voltmeter is attached to a parallel connection.
The simple circuit is redrawn with an ammeter.
They have high resistance.
The electric potential is the unit of electric potential.
The amount of energy per charge is determined by the amount of energy between the two points.
There are many terms used for this important concept in electricity.
If the ammeter and voltmeter are moved to different locations, there will be no observable difference in readings.
There is a slight difference in the emf between when the switch is open and closed.
The work done by the battery is reflected in the first emf.
The terminal emf is sometimes referred to as the internal emf.
When a battery dies, it doesn't run out of power, it runs out of energy.
The battery's voltage rating is a measure of how much energy the battery will give up to each charge.
Until the battery runs out of energy, it will continue to do so.
A simple electric circuit is illustrated with measuring devices.
Two observations can be made if a lightbulb is on for a long time.
The bulb gets hot because of the action of the electricity.
The heat of the bulb causes it to light up.
The current in the ammeter will decrease.
The idea of electrical resistance is linked to these two observations.
An electrical resistance is created by the interaction of flowing electrons and the molecule of a wire.
The resistance is dependent on the temperature, since an increase in temperature will increase the activity of the molecule and interfere with the flow of current.
Thermal energy is being converted to electrical potential energy.
The resistance that is desired in order for the bulb to do its job is the same resistance that is desired in the case of a lightbulb.
Resistance in a battery is unwanted and must be minimized.
In more complicated circuits, a change in current flow is required to protect devices, and so special resistors are made that are small enough to fit into a circuit.
Since insulators will stop the flow, we don't want to use them as resistance.
A range of materials is catalogued in electrical handbooks to assist scientists and electricians in choosing the right Resistivity for a given situation
The relationship between the voltage and the current in a circuit is revealed if the temperature can be maintained at a constant level.
This direct relationship was investigated by a German physicist, called Ohm's law.
In a circuit at constant temperature, the ratio of the voltage to the current remains constant.
The resistance of the circuit is represented by the slope of the line.
Some conductors don't obey the law.
Liquid conductors, lightbulbs, and Semiconductors do not.
The resistance of a conductor is affected by other factors.
The effects of temperature and material type are already discussed.
Resistivity is determined by the Greek letter r. The electrons try to move through the wire.
The resistance of the wire increases if the wire has a small cross-sectional area.
Increasing the length of the wire will increase the resistance of the wire.
The resistance factors all contribute to the resistance of the circuit.
The resistivity is usually rated at 20 degrees Celsius.
The resistivities of various materials are presented.
All lengths are in meters and areas are in square meters, since the ohm is a standard unit.
The copper wire is being used.
The wire is 1.2 m long and has a cross-sectional area of 8 m 2 at a constant temperature.
Light and heat can be produced using electrical energy.
Electricity can be used to turn a motor.
The amount of power and energy being produced can be determined by measuring the voltage and current in a circuit.
J/C is a measure of the energy supplied to each coulomb of charge in the circuit.
The total number of coulombs per second is measured by the current.
We know that the energy is given by VIt, where it must be in seconds.
The chapter is about to explore the laws of charge and energy.
The following rules for circuits were given to us by Gustav Kirchhoff.
The junction rule says that the total current coming into a junction must be equal to the total current leaving the junction.
As you travel around a closed loop of a circuit, the total voltage drops and gains must total to zero.
A voltage drop against the current is called a gain.
From positive to negative is a voltage gain and from negative to positive is a voltage drop.
The current coming into the junction on the left is 9 Amps, so a total of 9 Amps must be leaving.
Since the other two branches are carrying a total of 8 Amps, 1 Amp is left for the missing pathway.
I give you -2 V as a representation of the voltage dropping across the R 1 Resistor.
As we traced through this resistor from right to left, we were able to get the decrease in voltage result.
Two or more resistors are placed within a circuit.
An example is shown.
We need to ask some questions.
Imagine a series of doors, one after the other, as a way to think about this circuit.
People must wait to open another door as they exit one door.
The result is a decrease in the number of people leaving the room.
Adding more resistors in a series increases the resistance of the circuit.
All of these observations can be summarized as follows.
We have three currents in the resistors R 1, R 2 and R 3.
The source voltage V is more than 888-738-5526 888-738-5526.
The source voltage would be equal to one-third if all three resistors were equal.
The three currents are equal, so they can be canceled out of the expression.
The total resistance of the circuit increases as the number of resistances increases.
As more resistors are added, the current decreases.
The circuit current of 12/6 is 2 A since the source voltage is 12 V. The same current of 2 A can be used to determine the voltage across each Resistor.
When batteries are connected in series, the effective voltage increases as well.
A parallel circuit consists of pathways connecting from one point to another.
An example of a parallel circuit is shown.
I 1 and I 2 are split into a branch point in this circuit.
Experiments verify that the source V is the same as the source V across the resistors.
The current is shared and the voltage is the same.
Alternative paths are a feature of the parallel circuit.
Current can flow through the other path if one part of the circuit is broken.
The effect of adding resistors in parallel is to increase the effective circuit current by decreasing the circuit resistance.
Imagine a set of doors next to each other in a room.
The parallel-circuit analogy involves placing the doors next to each other.
The effect is to allow more people to leave the room even though there will be less people going through each door.
Reducing the circuit resistance and increasing the circuit current are the same thing.
These observations can be expressed as follows.
R 1 and R 2 have currents I 1 and I 2.
The expression indicates that the total resistance is determined "reciprocally", which reduces the total resistance of the circuit.
There is no effect on the overall voltages of the batteries if they are connected in parallel.
The 20- and 5-resistors are connected to each other.
If a 16-V battery is used, calculate the equivalent resistance of the circuit, the circuit current, and the amount of current flowing through each resistor.
It is easy to see that R eq is 4.
To find the current in each branch, we have to remember that the voltage drop across each Resistor is the same as the source voltage.
The total current is the same as expected.
A circuit that consists of resistors in parallel and series is presented.
The key to reducing such a circuit is to decide if it is a series or parallel circuit.
A parallel branch with two 4-resistors is placed in a series.
To determine the circuit current, the voltage reading in the voltmeter, and the current reading in the meter, you have to reduce the circuit to only oneresistor.
Reducing the parallel branch is necessary to find the circuit resistance R.
R e is the number of resistance.
The circuit can now be thought of as a series of circuits between a 2- and 8-resistor.
In a series circuit, the same current flows through each resistor and the voltage drop across them is shared proportionally.
In a parallel circuit, the voltage is the same across all the resistors.
Since the two resistors are equal, each will get half of the circuit current, and the reading on the ammeter is 1 A.
We used the rule at the junction to reduce the current.
Questions on the AP physics 1 exam will be limited to one parallel path and one ideal battery in circuits.
Many students of physics are confused by the fact that the current coming out of the resistor is the same as the current coming in.
Many students think the energy of moving electrons is a type of energy called kinetic energy.
The moving charges carry the electrical potential energy in the electric and magnetic fields.
The electrons going into the resistor are different from the ones coming out.
The fields associated with their relative positions are completely different even though the number of electrons passing per second is the same.
All potential energies are related to the physical relationship between two or more objects.
The slightly closer-spaced electrons before they enter the Resistor have more energy than the slightly farther apart electrons leaving the Resistor, just as 5 fully extended rubber bands moving past you at 5 mph have more total energy than the same 5 slack rubber bands moving past you at the same speed
The strongest example of field energy for electricity is in light.
As the light goes from one place to another, it is carrying energy.
There are other potential energies that can be used to make parallels.
The rock's potential is stored in the field between the rock and the Earth.
The block at the end of the spring does not hold the elastic energy of a stretched spring.
Positive and negative electric charges exist.
Electrons have a negative charge.
There is a positive charge.
Like charges repel, unlike charges attract.
The presence of static charges can be detected with an electrical device.
The objects are charged by the transfer of electrons.
The force between two static charges is described by Coulomb's law.
The force of attraction is proportional to the product of the charges and the force of repulsion is proportional to the square of the distance between them.
The law of gravitation is similar to this one.
The electrical potential difference is equal to the work done per unit charge.
Electric current is the flow of charge in units of amperes.
The conventional current is based on a positive charge flow.
At constant temperature, the ratio of voltage and current is a constant in a conductor.
The material used, length, and cross-sectional area are all related to electrical resistance.
Ammeters measure current and are placed within a circuit.
The potential difference is measured and placed in parallel across segments of the circuit.
A source of potential difference is needed for a simple circuit.
Resistors connected in series have the same resistance as their numerical sum and carry the same current through each.
The same potential difference can be experienced across parallel Resistors if they are connected in parallel.
The flow of current in circuit branches and the changes in voltage around loops are described in the rules.
There are several techniques for solving electric circuit problems discussed in this chapter.
Series and parallel circuits are used for resistances with one source of emf.
The determination of currents within the circuit and the potential drops across the resistors are measured by the Ohm's law.
Try to reduce all subbranches first when working with a combination circuit.
The goal is to be able to identify the missing quantities by using Ohm's law.
If you don't have a sketch of the circuit, you need to.
The direction of current is taken from the positive terminal.
A is charged to a value of Q elementary charges.
A neutral insulated metal sphere is touched and separated from it.
The neutral insulated metal sphere C is touched to the second sphere.
spheres A and C are separated after being touched.
10 A of current is present in a 20-resistor.
One source of negligible internal resistance is the only source of emf connected to the 5- and 10-resistors.
Four lightbulbs are arranged in a circuit.
Four point charges are arranged in the same way as shown below.
A rod attracts a sphere.
Platinum wire is wound into a coil.
A laboratory experiment uses lightbulbs.
The current readings decline after a while.
Sphere A and B have zero charges.
Each sphere will have half of the total charge when it is touched and separated.
Each now has + Q.
We distribute the charge evenly when B and C are touched.
B, C, and A all have + Q /4.
When A and C are touched, we take the average of + Q /4 and + Q /2, which is +3 Q /8.
The final distribution is 3 Q -8, Q -4, and Q -8.
Everything except one charge is given.
The charge is equivalent to 10 18 electrons.
2 A for 2 s is equivalent to 2.5 x 10 19 electrons.
The two resistors are in a series.
R is 4.
The source current must be added to the branch currents.
We can see that the current in the 2-resistor is 6/2 because of the Ohm's law.
The current in R must be equal to 1 A.
The 10-resistor has twice the resistance of the 5-resistor in series.
When the circuit is on, the 10-resistor will generate twice as much energy as if the currents were equal.
There will be a greater potential difference across D than across the equivalent resistor.
The equivalent resistance will generate less power than the currents will allow.
With the current split for the parallel part, there will be less energy available for the resistors A, B, and C. Bulb D will be bright.
The lower- left-corner charge will experience mutual repulsions from the other three since all the charges are positive.
Coulomb's law gives the magnitude of each force.
The Pythagorean theorem was used to determine the diagonal distance.
F-1 acts to the left and F3 acts to the right.
F-2 acts at an angle to the lower left.
To find the angle, we have to use the sides of the rectangle.
F-2 will be negative by our sign convention.
The net force acting on the lower left corner charge is the sum of the charges.
The ph is relative to the x - axis.
The only conclusion you can make is that the sphere is neutral or oppositely charged.
The charges are distributed around the outside of the car if it is hit by lightning.
This acts like a shield.
R is the resistance needed.
The cross-sectional area is what we need.
There is an equivalent resistance of 8 O + 2 O.
The resistance is in close proximity to the other one.
5 is the equivalent resistance for the entire parallel branch.
The total equivalent resistance of 10 is made up of this resistance and the other 5-resistors.
There is a potential difference of 20 V between the parallel branch's resistance and that of the entire branch, because the parallel branch's resistance is also 5.
The potential difference is the same across the circuit.
The 10-resistor has 20 V across it.
We find that this means a current reading of 2 A for ammeter A.
The emf of the system is not changed when two batteries are connected in parallel.
Since the parallel connection of the two batteries is similar to the parallel connection of two capacitors, the storage capacity of the battery system is increased.
The equivalent resistance of 1 can be achieved by connecting two 2-resistors.
An equivalent resistance of 3 can be achieved by connecting two 2-resistors in parallel and then one 2-resistor in a series.
Lightbulbs produce their energy by heating up the inside of them.
Since the resistance has increased, this increase in temperature reduces the current flowing through them.