In solid conductors, electric current is the flow of
electrons
Electrons move in an electric circuit
by interacting with an established electric field
An ampere is a
unit of current
An example of a voltage source is
a dry cell, a generator, a car battery, rubbing a rubber rod with fur.
Electrical resistance in a wire depends on the wire's
thickness, conductivity, length.
Compared to thin wires, electrical resistance in thick wires is
less
For most conductors, as their temperature increases, their resistance
increases
Electrical resistance is measured in
volts,joules,watts,amperes
none of the above
A woman experiences an electric shock. The electrons making the shock come from
the woman's body
A pulsating electric field can travel through a wire at a speed of
the speed of sound waves in metal
A wire carrying a current is normally charged
not at all
The primary reason a bird can perch harmlessly on bare high voltage wires is that
there is no potential difference across the bird's feet
Alternating current is made by
alternating the direction of voltage of the power source
The frequency of AC current in North America is
60 hertz.
Current from a battery is always
DC
The net speed of electrons in a wire is about
0.01 cm/s.
Where do the electrons come from that produce heat and light in a light bulb?
the bulb's wire filament
In 2004, the number of electrons delivered to an average American home by an average power utility was
zero
When we say an appliance uses up electricity, we really are saying that
electron kinetic energy is changed into heat and other forms of energy
If you plug an electric toaster rated at 110 V into a 220-V outlet, current in the toaster will be
twice what it should be
Electric power is defined as
current times voltage.
Power outlets in our homes typically have a potential difference of
120 V
When an 8-V battery is connected to a resistor, 2 A of current flows in the resistor. What is the resistor's value?
4 ohms
The current through a 5-ohm resistor connected to a 150-V power supply is
30 A
A 15-ohm resistor has a 5-A current in it. What is the voltage across the resistor? a. 5 V
more than 25 V
What is the resistance of a toaster that uses 5 A of current when connected to a 120-volt power source?
24 ohms
When connected to a 110-volt power supply, how much current is in a light bulb that has a resistance of 220 ohms?
0.5 A
If you accidentally grabbed the prongs of a partially plugged-in 120-V electrical plug on a day when your skin resistance was 130,000 ohms, how much current would pass through your body?
0.0009 A
Electrical resistance is measured in
volts, amperes, joules, watts
none of the above.
A closed circuit is a circuit in which charge
can flow
The symbol used to represent resistance in a schematic diagram is
a zigzag line
When resistors are put in series next to each other, their overall resistance is
larger than the resistance of any individual resistor
When resistors are put in parallel with each other their overall resistance is
smaller than the resistance of any of the resistors
As more lamps are put into a series circuit, the overall current in the circuit
decreases
As more lamps are put into a parallel circuit, the overall current in the circuit
increases
Compared to the resistance of two resistors connected in series, the same two resistors connected in parallel have
less resistance
When one light bulb in a series circuit containing several light bulbs burns out
none of the other bulbs will light up
When one light bulb in a parallel circuit containing several light bulbs burns out, the other light bulbs
burn the same as before
In a simple parallel circuit
voltage across each branch is always the same
Electrical devices in our homes are connected in
parallel
Fuses and circuit breakers are used to
protect us, prevent overloading, keep wires from getting overheated, break the circuit when too much current is being used
all of the above
In order for current to flow in a circuit, you must have
a complete path for the current
When two light bulbs are connected in series, the
same amount of current always flows through each bulb
What is electrical resistance? What characteristics of a wire determine its resistance? How does resistance normally vary with temperature?
Electrical resistance is the resistance a conductor offers to the general movement of electrons. Resistance of a wire depends on what material the wire is made of as well as the dimensions of the wire. Resistance increases with temperature.
What is the difference between direct current and alternating current? When we plug a light bulb into a wall outlet, where do the electrons come from?
In a direct-current circuit the polarity of the source never changes, whereas in an alternating-current circuit the source polarity changes at a fixed rate, typically 60 times per second. When we plug a light bulb into the wall outlet, the electrons that