Chapter 23 Electric Current

Two objects were initially neutral. After they were rubbed against each other, it is determined that one of them has n electrons in excess. What can you say about the charge of the second object? (There may be more than one right answer.)

-It has an excess positive charge. -It is missing n electrons. Submit

Resistors in series

-same current travels through all the resistors (I1 = I2 = I3) - voltages add -resistances add (Requivalent = R1 + R2 + ...) -As the e- flow through each resistor, there is a voltage drop in each resistor V = V1 + V2 + ... -Equivalent resistance is the sum of individual resistances (increases as more resistors are added in series)

One ampere is a rate of flow equal to

1 coulomb of charge per second. Recall that 1 coulomb, the standard unit of charge, is the electric charge of electrons. In a wire that carries 5 amperes, for example, 5 coulombs of charge pass any cross-section in the wire each second.

At what would it cost to operate a 1200-W hair dryer for 1 h?

18 CENTS 1200 W= 1.2 W so 1.2kW*1 H* .15 cents/kWh=18 cents

parallel circuit

A closed electrical circuit in which the current is divided into two or more paths and then returns via a common path to complete the circuit.

Open Diode

A diode that has a high (infinite) resistance in both directions.

atomic lattice

A large three-dimensional arrangement of atoms held together by covalent bonds.

Conductors and Insulators

Conductors - materials through which electric charges can easily flow Insulators - materials through which electric charges do not move easily

The greater the voltage the greater the_______

Current

Power=

Current x voltage

alternating current

Electric Current that repidly reverses in direction. The electric charges vibrate about relatively fixed positions, usually at the rate of 60 Hz in North America.

direct current

Electric current in which the flow of charge is always in one direction ***a battery produces direc current in a circuit becasue each terminal of a battery always has the same sign***

conduction electrons

Electrons in a metal that are free to move around in the metallic crystal lattice.

But, If the resistance of the circuit is doubled, the current will be_______

Half what it would be otherwise. ***The greater the resistance, the smaller the current/.

LED

Light Emitting Diode

When electrons flow in a thin lamp filament, they experience "friction." What is the practical outcome of this?

When electrons flow in a thin lamp filament, they experience "friction." What is the practical outcome of this?

Resistors in parallel

When resistors are in a parallel circuit, the total resistance of the circuit is less than the resistance of the individual resistors as there are now more paths for current.

When we say that charge flows, we mean that charged particles flow. Charge is a property of particular particles, most significantly electrons, protons, and ions

When the flow is of negative charge, electrons or negative ions constitute the flow. When the flow of charge is positive, protons or positive ions are flowing.

How much current exists depends not only on the voltage but also on the

electrical resistance the conductor offers to the flow of charge

What unit is represented by joule per coulomb?

volt

the quantity used up in a circuit is______?

energy

Thick wires have less resistance than thin wires. Longer wires ________

have more resistance than short wires.

less current at the same voltage means

less power

The damaging effects of electric shock are the result of current

passing through the body

generator or chemical batteries are suitable_____

pumps in electric circuits and can maintain a steady flow. ****Batteries and electric generators steadily do work to pull negative charges away from positive ones.*****

a capacitor acts as a_____

storage reservoir for charge. a capacitor produces a retarding effect on changes in the flow of charge. It opposes changes in voltage and smoothes the pulsed output.

Electrical resistance also depends on________

temperature

potential difference

the difference in electrical charge between two points in a circuit expressed in volts ***Without a potential difference, no charge flows.

drift velocity

the net velocity of a charge carrier moving in an electric field

electric power

the rate at which electrical energy is converted to another form of energy, heat, or light.

thermalenergy

the total energy of the particles that make up any matter

The resistance of a wire depends both on the __________ and___________ of the wire and on its particular conductivity.

thickness and length

You are holding a positive charge and there are positive charges of equal magnitude 1 mm to your north and 1 mm to your east. What is the direction of the force on the charge you are holding?

to the southwest ***The total force is determined by the vector addition of the force from the north charge and the force from the east charge. However, because both charges are the same magnitude and the same distance away from you, the forces are also the same magnitude. Therefore, the net force is the vector sum of the two and the direction of the force on the charge you are holding should be to the southwest (equally to the west and the south).

series circuit

An electric circuit with a single path

Resistor

An electrical device that resists the flow of electrical current

What causes electric shock: cureent or voltage?

Although electric shock occurs when current is produced in the body, impressed voltage causes the current. So in this sense, voltage causes shock.

The rate of electrical flow is measured in

Amperes

Four ++2 μC�C charges are placed at the positions (10 cmcm, 0 cmcm), (−−10 cmcm, 0 cmcm), (0 cmcm, 10 cmcm), and (0 cmcm, −−10 cmcm) such that they form a diamond shape centered on the origin. A charge of ++5 μC�C is placed at the origin. If the force between a ++2 μC�C and a ++5 μC�C charge separated by 10 cmcm has a magnitude of 9 NN, which of the following can we say about the force on the ++5 μC�C charge at the origin in this case?

Many times it is possible to find the force on a charge due to other charges without doing any calculations by simply considering the symmetry of the arrangement of charges. In this case, there is mirror symmetry across both the x axis and the y axis so there can be no net push or pull in either of those directions.

Without a potential difference...

No charge flows

If the two feet of a bird on the high-potential wire of a power line are widely spaced, won't it get a shock?

No, because there is no appreciable difference in electric potential between its feet.

Georg Simon Ohm (1789-1854)

Ohm's Law: V=IR The SI unit of electrical resistance, the ohm (symbol ), is named after him.

electric current

The continuous flow of electric charges through a material

electromagnetic induction

The phenomenon of producing a voltage in a conductor by changing the magnetic field near the conductor. If the magnetic field within a closed loo changes in any way, a voltage is induced in the loop. The induction of voltage is actually the result of a more fundamental phenomenon: the induction of an electric field. Faraday's Law.

electrical resistance

The property of a material that resists the flow of charged particles through it; measured in ohms

Electron Drift Speed

The speed at which electrons move through a conductor. (Very slow)

Charged flow only when______

They are oushed or pulled

Volt

Unit of electric pressure

Is the voltage between two points in an electric circuit related to the flow of electrons between the points?

Yes

A potential difference across the ends of a wire produces current. Instead of saying potential difference, can we as well say voltage?

Yes. electrical potential and voltage are interchangeable terms. We now consider the difference in electric potential between two points in a conducting path, also measured in units of volts.

Voltage Drop

a decrease in voltage along a conductor through which current is flowing

voltage source

a device that creates a potential difference in an electric circuit

What unit is represented by coulomb per second?

ampere

The rate of electrical flow is measured in

amperes

We often think of current flowing through a circuit, but don't say this around somebody who is picky about grammar because the expression "current flows" is redundant. More properly_______

charge flows—which is current.

Voltage is electrical pressure that doesn't flow anywhere; it is the

charges that flow

analogous

comparable