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53 terms

Physics 101 Part 3

STUDY
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In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus.
Strip electrons from an atom and the atom becomes a
positive ion.
The electrical force between charges is strongest when the charges are
close together.
When a car is struck by lightning, the resulting electric field inside the car is
zero.
Electric potential, measured in volts, is the ratio of electric energy to amount of electric
charge.
When the distance between two charges is halved, the electrical force between the charges
quadruples.
The direction of an electric field is the direction of the force that the field would exert on
a proton.
If you use 10 J of work to push a coulomb of charge into an electric field, its voltage with respect to its starting position is
10 V
An electroscope is charged positively as shown by foil leaves that stand apart. As a negative charge is brought close to the electroscope, the leaves
fall closer together
In the unlikely case of a lightning strike, it is worse to be inside a building framed with
wood
Two charged particles attract each other with a force F. If the charges of both particles are doubled, and the distance between them also doubled, then the force of attraction will be
F
Two charged particles held close to each other are released. As they move, the force on each particle increases. Therefore, the particles must have
opposite signs.
An ampere is a unit of electrical
current.
The current through a 10-ohm resistor connected to a 120-V power supply is
12 A.
A 10-ohm resistor has a 5-A current in it. What is the voltage across the resistor?
more than 20 V
When a 10-V battery is connected to a resistor, the current in the resistor is 2 A. What is the resistor's value?
5 ohms
Alternating current is normally produced by a
generator
The electric power of a lamp that carries 2 A at 120 V is
60 watts.
When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is
less than the resistance of either lamp.
On some early automobiles both headlights went out when one bulb burned out. The headlights must have been connected in
series
A 100-Watt lamp glows brighter than a 25-Watt lamp. The electrical resistance of the 100-Watt lamp must be
less
In an electric circuit, the safety fuse is connected to the circuit in
series.
Two lamps, one with a thick filament and one with a thin filament, are connected in series. The current is greater in the lamp with the
the same in each lamp
Two lamps, one with a thick filament and one with a thin filament, are connected in parallel to a battery. The voltage is greatest across the lamp with the
Both voltages are the same.
If 0.8 A of current flow through a light bulb connected to a 120 V outlet, the power consumed is
96 W
A 60-W light bulb and a 100-W light bulb are each rated at 120 V. Which light bulb has a larger resistance?
the 60-W bulb
A 60-W light bulb and a 100-W light bulb are connected in series to a 120 V outlet. Which light bulb has more current in it?
Both have the same current.
An electric heater is rated at 300 W when used in a 110-V circuit. The safety fuse in the circuit can handle 15 A of current. How many heaters can be safely operated in the circuit?
5
The source of all magnetism is
moving electric charge.
Like kinds of magnetic poles repel while unlike kinds of magnetic poles
attract.
An iron nail is more strongly attracted to the
north or south pole - no difference really.
Magnetic field lines about a current-carrying wire
circle the wire in closed loops
The force on an electron moving in a magnetic field will be the largest when its direction is
perpendicular to the magnetic field direction.
Which pole of a compass needle points to a south pole of a magnet?
north pole
Outside a magnet, magnetic field lines are conventionally drawn from
north to south
When there is a change in the magnetic field in a closed loop of wire
all of these
The magnetic field strength inside a current-carrying coil will be greater if the coil encloses a
rod of iron.
A device that transforms electrical energy to mechanical energy is a
motor.
A transformer actually transforms
voltage.
The primary of a transformer is the coil connected to
the power line
Transformers use ac so there will be the required
change in magnetic field for operation.
Compared to the primary voltage, the secondary voltage may be
larger, smaller, or the same.
The output power of an ideal transformer is
equal to the input power.
A certain transformer doubles input voltage. If the primary coil has 10 A of current, then the current in the secondary coil is
5 A.
Neon signs require about 12,000 volts to operate. If the circuit uses a 120-volt power source, the ratio of primary to secondary turns on the transformer should be
1:100
The voltage across the input terminals of a transformer is 110 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer puts out
55 V.
Four amperes of current exist in the primary coil of a transformer. The voltage across the primary coil is 110 V. What is the power output of the secondary coil?
440 W
A 60 watt light bulb uses _____________ of electrical energy in five seconds.
300 joules
Five 20 Ω resistors are connected in parallel. The equivalent (total) resistance of this circuit is ______________ .
4 Ω
The standard of resistance is
ohm
As more bulbs are added in series, the current from the battery ____________ and the current through the bulbs _______________ .
decreases, decreases
Resistor A has a larger resistance than resistor B. When they are placed in parallel, the voltage drop across A is ____________ the voltage drop across B.
the same as
Four identical light bulbs are connected in parallel across a battery which provides 12 A of current. If one of the bulbs burns out the battery will provide ___________ of current and the current through each bulb will be ______________ .
9 A, 3 A