Flow of Charge

What is the relationship among the units of measurement for the three quantities related by Ohm's law?

1 ampere = 1 volt/ohm

Express the equation electrical power=current x voltage.

1 watt = 1 ampere x 1 volt

What is the standard voltage of AC in the United States?

110-120 V

If 120 volts AC are impressed on a lamp, then an average of ________ joules of energy are dissipated by each coulomb of charge that is made to vibrate.

120

One kilowatt-hour is the amount of energy consumed in _______ hour at the rate of _________ watts.

1; 1000

What is the purpose of the third prong on a three-prong electric plug?

3rd prong is connected to the ground to prevent electrical shock

If the power and voltage on a lightbulb read "60 W, 120 V," how much current will flow through the bulb?

60/120 = .5 A

Explain what would happen if a Van de Graaff generator charged to a high potential was connected to a ground wire.

A surge of charge would flow through the wire. The flow would be brief because the sphere of the generator would quickly reach a common potential with the ground.

With an ______________, you can operate a battery-run device on AC instead of batteries.

AC-DC converter

The current in laptops and cellphones is _______.

DC

Explain what happens in your body when you are jolted by an AC electric shock.

Electrons do not come out of the wire and through your body and into the ground; energy does. The energy simply causes free electrons in your body to vibrate in unison.

T/F: The amount of charge that flows in a circuit does not depend on the voltage provided by the voltage source.

False

In a AC circuit, do the conduction electrons make any net progress in a single direction?

No, in a single cycle the electrons drift a tiny fraction of a centimeter in one direction, and then the same tiny distance in the opposite direction.

What is a voltage source?

Something that provides a potential difference.

Define electric power.

The rate at which electrical energy is converted into another form (mechanical energy, heat or light).

What is electric resistance?

The resistance that a conductor offers to the flow of charge.

What are resistors?

They are elements in a circuit that are used to regulate current.

T/F: Electric resistance depends on the temperature of the wire.

True

T/F: The potential energy per coulomb of charge available to electrons moving between terminals of a battery or generator is the voltage.

True

T/F: The resistance of a wire depends on the conductivity of the material used in the wire.

True

A 60-hertz current means that the current ...

alternates back and forth 60 cycles per second

What is equivalent to 1 coulomb of charge per second?

ampere

What is the SI unit used to measure electric current?

ampere

The source of electrons in a circuit is the ...

conducting circuit material itself

What are the particles within a solid conductor that carry charge through a circuit?

conduction electrons

The damaging effects of electric shock are the result of ___________ passing through the body.

current

How can your express Ohm's law mathematically?

current = voltage/resistance

In addition to a transformer to lower the voltage, an AC-DC converter uses a _______, which acts as a one-way valve to allow electron flow in only one direction.

diode

In a current-carrying wire, collisions interrupt the motion of the electrons so that their actual _____________, or net speed through the wire due to the field, is extremely low.

drift speed

What is the flow of an electric charge?

electric current

When you plug a lamp into an AC outlet, ___________ flows from the outlet into the lamp, not __________.

energy; electrons

T/F: The resistance of your body is much greater when you're soaked with water than when your skin is dry.

false

When you turn on an electric lamp, what two forms of energy are produced?

heat and light

Electric resistance is measured in units called ________.

ohms

Charge flows when there is a ________________ between the ends of a conductor.

potential difference

The relationship among current, voltage, and ____________ is called Ohm's law.

resistance

The resistance of some materials becomes zero at very low temperatures, a phenomenon known as ___________.

superconductivity

Charges flow _________ a circuit because of an applied voltage _________ the circuit.

through; across

T/F: A battery produces direct current.

true

T/F: A bird perched on a high-voltage wire is not shocked because there is not a potential difference between one part of its body and another part.

true

T/F: A pulsating electric field can travel through a circuit at nearly the speed of light.

true

T/F: AC is current that repeatedly reverses direction.

true

T/F: Direct current refers to a charge that always flows in one direction.

true

T/F: Energy is transported through connecting wires of circuit at nearly the speed of light.

true

Electrical power = current x

voltage

What is the net charge in a current-carrying wire?

zero