PY 131 Chapter 23 Conceptual Academy

A battery works as

an electric potential pump.

The drift speed in an electric current is about

300 meters per hour.

Voltage is

energy per charge.

Voltage can be thought of as an electrical

pressure.

High voltage only mean a lot of current if the

reistance is low.

The current in an electric bulb depends on the

voltage across the bulb divided by the filament resistance.

It is best to say that voltage is established across a bulb, and charge flows

through a bulb.

Which form of Ohm's law is preferred in this lesson?

I = V/R

The North American standard consumer voltage is at about 120 volts, which is

less efficient than 220 volts.

AC is prefered for energy transmission because it can be effectively

All of these.

This lesson makes the point that electrons are

already in the wires of an electric circuit.

Examples of electric power in this lesson include

light-bulb circuits.

As Paul adds more light bulbs in series, the voltage across the two terminals of the battery

stays the same.

As Paul adds more light bulbs in series, the voltage across each light bulb

decreases.

As Paul connects more light bulbs in parallel, the resistance experienced by the battery

decreases.

This lesson treats the flow of

both of these

A flow of electric charge in a wire normally requires a

potential difference across the ends of the wire.

A voltage source in a circuit provides electrical

pressure.

The electric resistance in a length of wire is doubled when the wire is

twice as long.

When your body undergoes electric shock, the source of moving electrons is

electrons already in your body.

Electrons in the filament of a lamp that carries ac have a net speed that is

zero.

The entity that travels about the speed of light in an electric circuit is

electric field.

Electric power in a circuit is the rate at which

energy dissipates.

When the filament breaks in one lamp in a series circuit, other lamps in the circuit normally

go out.

When the filament breaks in one lamp in a parallel circuit, lamps in other branches of the circuit normally

continue glowing as brightly.

What is the combined resistance of a 4 ohm and 6 ohm resistor connected in parallel?

2\.4 ohms.

For charge to continue flowing between two points of a conductor, what must you have?

NOT A steady magnetic field

What happens to the electrical resistance in a copper wire as it is heated?

Electrical resistance increases.

How is an electrical diode useful?

For changing ac to dc.

When connected in series to a 120 volt circuit, which has the greater current: a 50 watt light bulb or a 100 watt light bulb.

Both have the same resistance.

Two resistors are placed in series. How does this compare to the same two resistors placed in parallel?

In parallel there is less resistance.

What electrical resistance does a battery experience when the two lamps of the circuit are connected in parallel?

Less than the resistance of either lamp.

A lamp in a circuit carrying 2 amps attached to a 120 voltage source has how much electric power?

240 watts

Within a circuit having a current of 5 amps there is a 10 ohm resistor. What voltage is there across the resistor?

more than 20 V

What do we really mean when we say that a kitchen appliance uses up electricty?

Electron kinetic energy is changed into heat.

What happens to the resistance of a copper wire after being stretched thinner?

Electrical resistance increases.

How does the current within the filament of a lamp compare to the current in a wire connecting to that lamp?

The current in the wire is the same.

What electrical resistance does a battery experience when conncted to two lamps in series?

More than the resistance of either lamp.

A magnified holographic image can be accomplished when viewed with light having a

longer wavelength than the original light.

How are the radio, fan, and headlights of a car connected electrically?

In parallel with a switch for each.

During the early 1990s, the average number of electrons delivered daily to the average American household was

zero.

Two identical light bulbs in a series circuit draw a current of 0.25 amps while there is a 110 voltage across both bulbs. What is the resistance of each bulb?

220 ohms.

What happens to the electric field within an AC circuit?

It changes magnitude and direction with time

You know a 100 watt light bulb glows brighter than a 50 watt light bulb. But which bulb has the higher electrical resistance?

The 50 watt bulb has a higher resistance.

What happens to the current within a power source as more lamps are attached in a series circuit?

The current decreases.

A hologram employs the principle of

both of these

How much greater would be overall resistance be if a 1 ohm, 2 ohm, and 3 ohm resister were placed in series rather than in parallel?

11 times as great.

What electical device does a circuit breaker substitute for?

A fuse.

What is the combined resistance of two 1 ohm resisters in series and in parallel?

2 ohms in series and when in parallel, 1/2 ohm.

How does charge flow in a circuit powered by a battery?

Through both the battery and the rest of the circuit.

What power dissipates as 3 amps crosses a 4 ohm resistor?

36 W.

When connected in series, which is the current greater: the thick lamp filament or the thin lamp filament?

The current is the same in each lamp.

Should a safety fuse be connected to a circuit in series or in parallel?

In series.

How much power dissipates in a 2 ohm line carrying 80 amps of current?

12,800 W.

In the modern car, how are the headlights electrically connected?

In parallel.

A 120 watt lamp is connected to a 120 volt power source. What is the resistance within the lamp?

None of these

Which has a greater resistance: a 50 watt light bulb or a 100 watt light bulb (both rated at 110 volts).

The 50-W bulb

When a thick lamp filament and a thin lamp filament are connected in parallel, which experiences the greatest current?

There is greater current in the lamp with the thick filament.

What happens in a 120 volt circuit with a lamp in series?

120 joules of energy are given up by each coulomb of charge making up the current in the circuit.

What kind of current will you get in a toaster designed for 110 volts when plugged into a 220 volt outlet?

The current will be twice what it should be.

About what is the speed of electrons in a common DC circuit?

A fraction of a centimeter per second.

What is the normal charge on a wire carrying an electric current?

There's no charge at at all.

What is the cost of operating a 20 amp heater on a 110 volt circuit when the power is 10 cents per kilowatt hour?

$2.20.

When a thick lamp filament and a thin lamp filament are connected in series, which experiences the greatest drop in voltage?

There is a greater voltage drop across the lamp with the thin filament.

How many 300 watt electric hair dryers can be safely hooked up to a 110 volt circuit designed to accommodate no more than 15 amps?

**five**

How is a capacitor useful?

It smooths pulsed current.

Ten volts are applied across a resistor creating a current of 2 amps. What is the value of the resistor?

5 ohms

Within a circuit, a 120 volt potential is applied across a 10 ohm resistor. What current is flowing through the resistor?

12 amps.

What sort of current do you get when you plug a 60 watt light bulb into a 120 volt circuit?

0.5 A.

What is another name for the voltage drop across a piece of metal divided by the current passing through that piece of metal?

Resistance.

An aluminum dome holds a negative charge of 6.4 x 10(-7) coulombs. To make the dome neutral, how many electrons must be removed?

4\.0 x 10(12) electrons

What sort of power do you draw when a current flows at 0.8 A within a 120 volt circuit?

96 W.

What gives the energy to the moving charges in a light bulb circuit?

A generator.

The filament of an incandescent light bulb contains electrons. Once the filament starts to glow, from which electrons does the glowing occur?

From the same electrons that were in the filament when the light was off.

What does a capacitor store?

Both charge and energy.

What flows through a circuit?

Charge flows in a closed circuit.

A man gets shocked electrically. From where did the electrons shocking the man come from?

The man's body.

Must a wire be charged to carry an electric current?

It may or may not be electrically charged.

How does the thickness of a 100 watt incandescent light bulb compare to that of a 60 watt incandescent light bulb?

The 100 watt bulb has a thicker filament.

How is an alternating current normally produced?

By a generator.

What happens to the current within a power source as more lamps are attached in a parallel circuit?

The current increases.

When a thick lamp filament and a thin lamp filament are connected in parallel, which has the greater voltage drop?

The voltage drop across each lamp is the same.

What causes electrons to flow within a wire?

A potential difference across its ends.

When add another lamp to a parallel circuit, what happens to the overall current?

The current increases.

Between a faulty 120 volt fixture and a 120,000 volt Van de Graaf generator, which is more dangerous?

Touching the faulty light fixture is more dangerous.

When add another lamp to a series circuit, what happens to the overall current?

The current decreases.

What is the main source of electrons in an electrical circuit?

The electrical circuit itself.

What is an "ampere"?

An electrical unit of current.

Simply stated, a hologram is a

complex diffraction grating.

How do electrons move in an electrical circuit?

By interacting with an established electric field.

A lamp is turned on in a DC circuit. What is the average speed of the electrons within the lamp?

Less than 1 cm/s.

Connect a pair of lamps in series and you draw current from the connected battery. Connect the same lamps in parallel and you draw. Two lamps in series draw a current from a connect battery. If the lamps were instead placed in parallel, how would the current compare?

In parallel there is more current.

Where do the electrons that light up an incandescent lamp come from within an AC circuit?

The atoms in the light bulb filament.

How is the force of a steady magnetic field directed on a moving charge?

At right angles to the direction of the motion.

In an older model car a headlight burns out. Immediately the other headlight stops shining. How might those two headlights be electrically connected?

In series.