PHYS 1320 (Chapter 23)

What does the power company provide to our homes?

It provides energy to move the electrons.

What unit is represented by coulomb per second?

ampere

Two lightbulbs are hooked up to a battery in parallel. If one of the lightbulbs is disconnected, the other lightbulb will __________.

continue shining with the same brightness

A flow of electric charge in a wire normally requires a _________.

potential difference across the ends of the wire

The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is

12 ohms

The electric power supplied to a lamp that carries 2 A at 120 V is

240 watts.

What is the current in a bulb if the resistance of its filament is 2 ohms and it is connected across a 6-volt battery?

3 amps

An electric current of 5 amperes in a wire carries _________.

5 coulombs per second

What condition is necessary for the sustained flow of water in a pipe? What analogous condition is necessary for the sustained flow of charge in a wire?

A continuous pressure difference, often provided by a pump, is needed for water to flow. A continuous potential difference, often provided by a battery, is needed for charge to flow.

What condition is necessary for the flow of heat? What analogous condition is necessary for the flow of charge?

A difference in temperature is needed for heat to flow. A difference in electrical potential is needed for charge to flow.

Does electric charge flow across a circuit or through a circuit? Does voltage flow across a circuit or is it impressed across a circuit?

Charge flows through and voltage is impressed across a circuit.

What is the relationship between current, resistance, and voltage difference?

Current = Voltage Difference / Resistance

Why are electrons, rather than protons, the principal charge carriers in metal wires?

Electrons are free to move through the metal, whereas protons are fixed in place.

When you make your household electric payment at the end of the month, are you billed for voltage, current, power, or energy?

Energy

Using the formula power = current × voltage, find the current drawn by a 800-W toaster connected to 150 V .

I = 5.3 A

What is the function of the round third prong in a modern household electric plug?

It grounds the case to zero potential.

If the resistance of a circuit remains constant while the voltage across the circuit decreases to half its former value, what change occurs in the current?

It is cut in half.

If the voltage impressed across a circuit is held constant while the resistance doubles, what change occurs in the current?

It is cut in half.

Why does a wire that carries electric current become hot?

Moving electrons collide with atoms, which transfers their kinetic energy to atomic motion.

What is the unit of electrical resistance?

Ohm

What is the relationship among electric power, current, and voltage?

Power is current times voltage.

Then, using the equation current = voltage/resistance, find the resistance of the toaster.

R = 28 Ω

Does a battery produce dc or ac? Does the generator at a commercial power station produce dc or ac?

The battery is dc; the generator is ac.

How does the current change if you increase the resistance, keeping the voltage difference the same?

The current decreases.

What is the effect on the current in a wire if both the voltage across it and its resistance are doubled?

The current remains unchanged

If both are halved?

The current remains unchanged.

How does the resistance of a thick piece of copper wire compare to the resistance of a thin piece of copper wire?

The resistance of the thin piece is greater than that of the thick piece.

Will water flow more easily through a wide pipe or a narrow pipe? Will current flow more easily through a thick wire or a thin wire?

Wide pipe and thick wire

When a pair of identical lamps are connected in parallel

all of the above

What kind of current runs through the electric wiring in a home?

alternating current

The equivalent resistance of any parallel branch in a circuit is

always less than the resistance of the lowest resistor.

What factors does the resistance offered by a piece of conductor depend upon?

both the geometry and the material of the conductor

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

continue glowing as brightly

What type of field causes the electrons to do what they do in the wire?

electric field

What type of particle is responsible for a current flowing through a metallic wire?

electron

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

go out

What unit is represented by watt ⋅ second?

joule

A 100-W lamp glows brighter than a 25-W lamp. The electrical resistance of the 100-W lamp is

less.

The voltage across a 10-ohm resistor carrying 5 A is

more than 20 V.

When two lamps are connected in series to a battery, the electrical resistance that the battery senses is

more than the resistance of either lamp

The equivalent resistance of any series of resistors in a circuit is

none of the above

Of what physical quantity is Hertz a unit of?

number of times per second that the electrons move back and forth in the wire

One kilowatt is a unit of

power.

A lightbulb is labeled "100 watts." What does "100 Watts" represent?

the rate of energy being dissipated within the filament of the bulb when the bulb is on

What unit is represented by joule per coulomb?

volt