physics midterm chapter 8
The amount of current in an incandescent bulb rated 75W-120V is about
0.6 A.
The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in parallel is about
0.6 ohm.
An electron is pushed into an electric field where it acquires a 1-V electric potential. If two electrons are pushed the same distance into the same electric field, the electric potential of both electrons is
1 V
A pair of 1-ohm resistors connected in series is 2 ohms, and when connected in parallel is
1/2 ohm
It takes 10 J of work to push a charge initially at rest into an electric field. If the charge is then released, it flies back to its initial position with a kinetic energy of
10 J
If you do 10 J of work to push 1 coulomb of charge into an electric field, its voltage with respect to its starting position is
10 V
The current through a 10-ohm resistor connected to a 120-V power supply is
12 A
A power line with a resistance of 2 ohms draws a current of 80 A. The power dissipated in the line is
12,800 W.
Calculate the power of a hair dryer that operates on 110 V and draws a current of 15 A.
1700 W
A pair of 1-ohm resistors connected in series has a combined resistance of
2 ohms.
A 4-ohm and 6-ohm resistor connected in parallel have an equivalent resistance of
2.4 ohms.
The current through two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is
220 ohms
A length of wire has resistance R. The same kind of wire twice as long has resistance
2R
Two charged particles 1 m apart exert a 1-N force on each other. If the magnitude of each charge is doubled, the force on each particle will be
4 N
The value of a resistor that carries 2 A when connected to 10 V is
5 ohms
Three resistors take the shape of a triangle, one resistor in each leg. Resistance in one leg is 4 ohms, in a second leg is 6 ohms, and third leg is 10 ohms. A measurement of resistance across the 10-ohm resistor will show the equivalent resistance to be
5 ohms.
A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with
6 joules
The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about
6 ohms
How much energy is given to each coulomb of charge passing through a 6-V battery?
6J
What condition is necessary for a sustained flow of electric charge through a conducting medium?
A potential difference must be maintained across the medium, usually by an electrical "pump."
What is the function of the third prong on the plug of an electric appliance?
It is the ground plug and protects against stray voltages.
Two positively-charged plastic straws near each other tend to
Repel eachother
In a common dc circuit, electrons typically move at the speed of
a fraction of a centimeter per second.
A sustained flow of electric charge requires
a potential difference
Electric charge will flow in an electric circuit when
a potential difference exists
Which of these, all of the same length, has the greater electrical resistance?
a rubber rod
The unit of electric charge, the coulomb, is the charge on
a specific large number of electrons
Current that is typically 60 hertz is
alternating current
The electric charge of all electrons
are identical
An electron and a proton
attract each other.
Direct current is normally produced by a
battery
Normally a balloon charged to several thousand volts has a relatively small amount of
charge and energy
More current will occur in a lamp when its filament is
cold
As more lamps are put into a series circuit, the overall current in the power source
decreases.
Electrical resistance is greater for
dry skin
Which force binds atoms together to form molecules?
electric
Which flows through an electric circuit: voltage, electric charge, resistance, or all three?
electric charge
Every proton in the universe is surrounded by its own
electric field. gravitational field.
When we say an appliance "uses up" electricity, we are actually saying that
electrical energy changes to thermal energy.
A proton and an electron placed in an electric field experience the same force. Which undergoes the greater acceleration?
electron
The electric current in a copper wire is normally composed of
electrons
Lillian safely touches a 100,000-volt Van de Graaff generator. Although the voltage is high, the relatively small amount of charge means a relatively small amount of
energy transfer
The damage of electrical shock is predominantly due to
excess current
Alternating current is normally produced by a
generator
Just as water flows from high to low pressure, electric charge flows from
high to low voltage
A positive and a negative charge near each other are released. As they move, the force on each particle
increases.
Current in a conductor can be increased by
increasing the voltage across it. reducing its resistance.
When a steady voltage is across one-half as much resistance, the current
is doubled
Strictly speaking, it is correct to say that voltage
is impressed across a device in a circuit.
Charge carriers in a metal are electrons rather than protons because electrons are
loosely bound
When you scuff electrons from a carpet onto your shoes, you become
negatively charged
A balloon will stick to a wooden wall if the balloon is charged
negatively or positivley
Which of these does not have an electrical charge?
neutron
What is the difference between electric potential difference and voltage?
no difference
An electrical device that is "grounded" has
no potential difference between it and the ground.
Part complete A bird can sit harmlessly on a high-voltage wire because
no potential difference is across the birds feet.
When we say charge is conserved, we mean that charge can
only be transferred from one place to another
To achieve a low equivalent resistance for a pair of resistors, connect them in
parallel
If you strip electrons from an atom, the atom becomes a
positive ion
The purpose of a voltage source is to provide an electrical
pressure
When the distance between two charges is halved, the electric force between the charges
quadruples.
When you double the voltage in a simple electric circuit, you double
the current
Compared to the amount of electric current in the filament of a lamp, the amount of current in the connecting wire is
the same.
If you plug a 110-V electric toaster into a 220-V outlet, current in the toaster will be about
twice what it should be.
The electric field between oppositely-charged parallel plates is
uniform
Compared to the mass of a proton, the mass of an electron is
very much less.
When we think of electric potential difference, we are thinking about
voltage
The unit of measurement for electric power is
watts. joules per second.
The net electric charge on a current-carrying wire is normally
zero