2309 Chapter 4 Electricity

The amount of resistance of a particular conductor depends on four things: which are?

1. Materials: some materials allow a free flow of current because they have an abundance of free electrons, where as other materials have a tremendous resistance because they have virtually no free electrons. 2. Length: resistance is directly proportional to the length of the conductor; that is, a long conductor has more resistance than a short one. 3. Cross-sectional area: as a conductor with a large cross-sectional area has a lower resistance then one with a small cross-sectional area because there is a greater external surface area in which electrons can travel. (EX: thicker wire is like a 8 Line Freeway were thinner wire is like a one lane dirt road.) 4. Temperature: with metallic conductors, the resistance become greater as the temperature of the conductor rises.

What are the rules for a series circuit?

1. Total resistance is equal to the sum of the individual resistances. (R[t] = R[1]+ R[2] + R[3]) 2. All current elements are the same and equal to the total circuit current. (I[T] = I[1] = I[2]= I[3]) 3. Total voltage is equal to the sum of the individual voltages. (V[T] = V[1] + V[2] + V [3])

What are the rules for a parallel circuit?

1. Total resistance is the inverse of the reciprocals off of each individual resistance. 1/R[T] = 1/R[1] + 1/R[2] + 1/R[3] 2. Total current is equal to the sum of the individual current. I[T] = I[1] = I[2] = I[3] 3. The voltage across each current element in the same and equal to the total circuit voltage. V[T] = V[1] + V[2] + V[3]

What are the five general laws of electrostatic that are helpful in understanding the nature of electricity?

1. like charges repel and unlike charges of attract each other. 2. The electrostatic force between two charges is directly proportional to the product of their quantities and inversely proportional to the square of the distance between them (aka: Coulomb's law). 3. Electric charges reside only on the external surface are conductors. 4. The concentration of charges on a curved surface of a conductor is greater where the curvature is greatest. 5. Only negative charges (electrons) are free to move in solid conductors.

A 12 V battery moves 12 coulombs of charge. How much work is done? equation (1V = (1 J)/ (1 coulombs)

12V = (xJ)/(12 coulombs)= 144 J

For _________ ___________ The electrons flow in one direction and then flip and flow back in the opposite direction.

Alternating Current (AC)

_____________ is how we measure current.

Ampere

The __________ is defined as 1 coulomb flowing by a given point in 1 second or as The amount of current flowing with an electric potential of 1 volt in a circuit with a resistance of 1 ohm.

Ampere 1 ampere = (1 coulomb)/(1 second) 1 ampere = (1V)/(1ohm)

A ________ Is a device that produces electrons through a chemical reaction, stores an electric charge for the long-term, and provides an electric potential.

Battery

A _________ Is a device that is like a battery in that it stores and electric charge, but works very differently in that it cannot produce new electrons and stores they charge only temporarily.

Capacitor

__________ is a property of matter.

Charge

A ________ __________ Acts in the same manner as a fuse. If the current flow rises excessively, the circuit breaker's internal switch is tripped (opened), stopping the flow of electricity.

Circuit Breaker

Atoms That have a large number of free electrons and allow them to move are called ____________ ?

Conductors

Some materials, such as copper and gold, have a very large number of electrons free to move about, making them good ____________ for electricity.

Conductors

Electrical charges are measured in the system international (SI) unit____________ which is equal to the electrical charge of ________ x _______ electrons.

Coulomb / 6.25 x 10^18

__________ Is an expression of the flow of electrons in a conductor and is measured in amperes.

Current

A __________ (a solid state rectifier) Is a one-way valve device and allows electrons to flow in only One Direction.

Diode

For __________ __________ The electrons only flow in one direction.

Direct Current (DC)

_________ _______ is an inherent property of matter

Electric Charge

For Electric current to move, there must exist an ___________ __________, which is the ability to do work because of a separation of charges.

Electric Potential

_________ ___________ Is the ability to do work because of a separation of charges and is measured and volts.

Electric Potential

_________________ Is the study of electric charges in motion and what we most often consider as electricity.

Electrodynamics

What parts of matter have electrical charge?

Electron and Proton

________ Have one unit of negative charge

Electrons

The smallest unit of charge exist with the ________ and ___________

Electrons and protons

True or False: Amplitude is how we measure electric potential

False: Volts is how we measure electric potential

A _________ Is simply a section of special wire, usually encased in glass, that quickly melts if the current flow rises excessively, that's opening the circuit.

Fuse

Atoms that have a few free electrons are called ________ ?

Insulators

Glass and plastic, have very few free electrons, making them good ___________.

Insulators (glass, plastic, rubber, air, and wood)

________ Is how we measure resistance.

Ohm

The ________ Is defined as the electrical resistance equal to the resistance between two points along a conductor that, when I potential difference of 1 volt is applied, produces a current of 1 ampere.

Ohm 1 ohm = (1V)/(1 ampere)

A circuit in _____________ is one where the current divides into two or more paths before recombining to complete the circuit.

Parallel

For electric current to flow, there must be a _____________ difference between two electrodes and a suitable _________ through which it can travel.

Potential/ Medium

___________ ____________ Such as fuses and circuit breakers act as emergency devices that break or open the circuit if there is a sudden surge of electricity to the circuit or device.

Protective Devices

___________ Have one unit a positive charge

Protons

____________ Is that property of an element in a circuit that resists or impedes the flow of electricity and is measured in ohms.

Resistance

A __________ Is a device designed to inhibit the flow of electrons, thereby precisely regulating the flow of electricity through that part of the circuit where it is placed.

Resistor

A __________ is simply an adjustable or variable form of resistor.

Rheostat

Go look at the 2 charts in pictures and label them.

Same

A ________ Is a device that opens a circuit (breaks the pathway.)

Switch

What's does Ohm's law state?

That the potential difference (voltage) across the total circuit or any part of that circuit is equal to the current (amperes) multiplied by the resistance. V = (amperes) x(resistance) = I x R

A ____________ Is a device that can increase or decrease voltage by a predetermined amount.

Transformer

True or False: For a direct current the positive (+) and negative (-) do not change sides

True

True or False: If one has an abundance of electrons at one end of the wire and an abundance of positive charges at the other end (separation of charges), electrons will flow from abundance to deficiency.

True

True or False: Pathway for electricity must be closed (complete) for electricity to flow. But open circuit is one in which the pathway is broken, such as occurs when a switch is turned off.

True

True or False: Positive (+) and Negative (-) changes sides each half cycle.

True

True or False: a circuit in series is one where all the elements are connected in a single line along the same conductor.

True

Ohm's Triangle stands for?

V= voltage/ I= ampere/ R= resistance V I R

_______ is defined as the potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm (1V = 1 ampere x 1 ohm)

Volt

The _________ is also equal to the amount of work (in joules) that can be done per unit of charge.

Volt 1V = (1J)/(1 coulomb)

_________ is how we measure electric potential.

Volts

An _______ Circuit is a complex circuit that has different voltages and current flowing through different sections.

X-ray

What happens when you connect an AC circuit to a DC circuit?

You get High Voltage

________ _______ Is a closed pathway composed of wires and circuit elements through which electricity may flow.

electric circuit

________ is the study of stationary electric charges

electrostatics