Test 3
When a pair of identical lamps are connected in parallel
all of the above: current in each is the same, power dissipated in each is the same, AND voltage across each is the same.
When current reverses direction in a wire, the surrounding magnetic field
also reverses direction
Current that is typically 60 hertz is
alternating current.
The equivalent resistance of any parallel branch in a circuit is
always less than the resistance of the lowest resistor.
In units of measurement, power in watts is equal to
amperes x volts.
If a steady magnetic field exerts a force on a moving charge, that force is directed
at right angles to the direction of the motion.
The direction of the force exerted on a moving charge in a magnetic field is
at right angles to the direction of the motion.
Surrounding every moving electron is
both a magnetic field and an electric field
Ohm's law tells us that the amount of current produced in a circuit is
both of these: directly proportional to voltage AND inversely proportional to resistance
Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry
less current.
If two copper wires of the same length have different thickness, then the thicker wire has
less resistance.
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.
Electromagnetic induction occurs in a coil when there is a change in
magnetic field intensity in the coil.
Compared to a single lamp connected to a battery, two lamps connected in parallel to the same battery will carry
more current.
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.
Connect a pair of lamps in series and current is drawn from the battery. Connect the same lamps in parallel and the current drawn is
more.
A device that transforms electrical energy to mechanical energy is a
motor.
The source of all magnetism is
moving electric charge.
The equivalent resistance of any series of resistors in a circuit is
none of the above: NOT often less than the resistance of the lowest resistor, usually half the value of the lowest resistor, or always less than the resistance of the lowest resistor.
Which pole of a compass needle points to a south pole of a magnet?
north pole
Two charged particles held a certain distance apart are released. As they move, the force on each particle increases. Therefore, their charges have
opposite signs.
A beam of electrons passing through a magnetic field experiences maximum deflection if the direction of the beam is
perpendicular to the field lines.
The force on an electron moving in a magnetic field will be the largest when its direction is
perpendicular to the magnetic field direction
The safety fuse in an electric circuit is connected to the circuit in
series.
As the number of loops in a current-carrying wire is increased, the
stronger the enclosed magnetic field.
Two charged particles held a certain distance apart are released. As they move, the acceleration of each decreases. Therefore, their charges have
the same sign.
When a magnet is moved to and fro in a wire coil, voltage is induced. If the coil has twice as many loops, the voltage induced is
twice.
A transformer actually transforms
voltage.
To think of electric potential difference we are thinking about
voltage.
A 60-W light bulb connected to a 120-V source draws a current of
0.5 A.
When a light bulb is connected to a 4.5 V battery, a current of 0.12 A passes through the bulb filament. What is the resistance of the filament?
38 ohn
The resistors in the circuit shown each have a resistance of 600 Ω. What is the equivalent resistance of the circuit? _/\/\/\/\_ I I o-- I I ---------- I I / \ -\/\/\/\/- \ / / \ \ / o--------------------------
600 ohn
Two long, straight wires separated by 0.10 m carry currents of 18 A and 6 A in the same direction as shown. The current goes up. P is 0.05 m to the right of the right wire. What is the direction of the magnetic field at the point P?
Into the plane of the page
A wire is bent int the shape of a circle of radius r = 0.10 m and carries a 20.0-A current in the direction shown. The current goes clockwise. What is the direction of the magnetic field at the center of the loop?
Into the plane of the paper
The voltage across the input terminals of a transformer is 120 V. The primary has 50 loops and the secondary has 25 loops. The voltage the transformer delivers is
60 V.
The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in parallel is about
1 ohm.
The current in 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.
The voltage across the input terminals of a transformer is 120 V. The primary has 25 loops and the secondary has 50 loops. The voltage the transformer delivers is
240 V.
The electric power supplied to a lamp that carries 2 A at 120 V is
240 watts.
Each of the resistors in the circuit shown have a resistance of 160.0 Ω. What is the equivalent resistance of the circuit? o----/\/\/\/\-----/\/\/\/\-- I I \ I / I \ I / I o----/\/\/\/\----------------
400 ohn
The resistance of a filament that carries 2 A when a 10-V potential difference across it is
5 ohms.
The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about
6 ohms.
A coil of wire carries current I as shown in the figure. If the observer could "see" the magnetic field inside this arrangement of loops, how would it appear? I is a coil with the current coming from the right in a clockwise direction to the left, towards the observer. The coil is such so that the observer can see straight through the hole. A) Circles going in a counter-clockwise direction B) Circles going in a clockwise direction C) A set of Xs D) A set of dots E) Lines on the left going up, lines on the right going down
C) A set of Xs
Two loops carry equal currents I in the same direction. They are held in the positions shown in the figure and project above and below the plane of the paper. The point P lies exactly halfway between them on the line that joins their centers. The centers of the loops and the point P lie in the plane of the paper. Which one of the figures below shows the position of a compass needle if the compass were placed in the plane of the paper at P? Two loops are shown next to each other and parallel. Their currents are going forwards. A) S--N B) S I I N C) N I I S D) N--S E) S / / N
D) N--S
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 repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be
F/2.
Electric field lines begin on negative charges and end on positive charges.
False
If a 75 W bulb and a 100 W bulb are connected in series across a 120 V outlet, the 75 W bulb will dissipate 75 W of power and the 100 W bulb will dissipate 100 W of power.
False
If you double the diameter of a cylindrical wire, you double its conductivity but reduce its resistivity by one half.
False
Surrounding every stationary electron is a magnetic field
False
The force exerted on an electron moving in a magnetic field is maximum when the electron moves parallel to the magnetic field.
False
A long, straight wire is carrying a current of 5.0 A in the direction shown in the figure. The point P is 0.040 m from the wire. The current is going left. What is the direction of the magnetic field at point P due to the current in the wire?
Out of the plane of the page
A 9 V battery is hooked up to two resistors in series. One has a resistance of 5 Ω, and the other has a resistance of 10 Ω. Several locations along the circuit are marked with letters, as shown in the figure. Which statement is true? __________/\/\/\/\_____ _I_ 5Ω B I + _-_A I I I - I 10Ω C I D ---------/\/\/\/\--- The current at A is equal to the current at B, which is equal to the current at C, which is equal to the current at D. The current at A is greater than the current at B, which is greater than the current at C, which is greater than the current at D. The current at A is greater than the current at B, which is equal to the current at C, which is greater than the current at D.
The current at A is equal to the current at B, which is equal to the current at C, which is equal to the current at D.
Two loops carry equal currents I in the same direction. The loops are held in the positions shown in the figure and are then released. Which one of the following statements correctly describes the subsequent behavior of the loops? Two loops are shown stacked parallel to each other, both going counter-clockwise. The loops repel each other The loops attract each other The top loop moves to the right; the bottom loop moves to the right. The loops remain in the positions shown. Both loops move to the left.
The loops attract each other
Which one of the following statements concerning the magnetic field inside (far from the surface) a long, current-carrying solenoid is true? The magnetic field is non-zero and nearly uniform The magnetic field varies as 1/r as measured from the solenoid axis. The magnetic field is independent of the number of windings The magnetic field is independent of the current in the solenoid The magnetic field is zero.
The magnetic field is non-zero and nearly uniform
A wire, connected to a battery and switch, passes through the center of a long current-carrying solenoid as shown in the drawing. The drawing shows a solenoid coiling clockwise to the left, with a circuit through the middle. A switch is at the base, away from the solenoid. The solenoid is labeled I and the switch V. When the switch is closed and there is a current in the wire, what happens to the portion of the wire that runs inside of the solenoid?
There is no effect on the wire.
The amount of current produced by electromagnetic induction depends on the amount of induced voltage and the resistance of the circuit to which it is connected.
True
The current produced by a common generator is ac.
True
The force on an electron moving in a magnetic field will be least when its direction is the same as the magnetic field direction.
True
The force that acts between a pair of magnetic poles depends on magnetic pole strength and the separation distance.
True
The more closely electric field lines are packed together, the stronger the field.
True
When a bar magnet is thrust into a coil of copper wire, the coil tends to repel the magnet as it enters.
True
When a potential difference of 10 V is placed across a certain solid cylindrical resistor, the current through it is 2.0 A. If the diameter of this resistor is now tripled, the current will be 18 A.
True
Which one of the following statements concerning permanent magnets is false? The north pole of a permanent magnet is attracted to a south pole All permanent magnets are surrounded by a magnetic field. The direction of a magnetic field is indicated by the north pole of a compass Magnetic field lines outside a permanent magnet originate from the north pole and end on the south pole When a permanent magnet is cut in half, one piece will be a north pole and one piece will be a south pole.
When a permanent magnet is cut in half, one piece will be a north pole and one piece will be a south pole.
Electrons flow in a wire when there is
a potential difference across its ends.
Complete the following statement: The magnetic field around a current-carrying, circular loop is most like that of
a short bar magnet
The magnetic fields of a pair of nearby magnets can
add or subtract by vector rules.
Which statement is correct? resistance flows in a circuit all of the above voltage flows in a circuit charge flows in a circuit
charge flows in a circuit
The shape of a magnetic field surrounding a current-carrying conductor is
circular.
An ampere is a unit of electric
current.
The electric field at point P due to a point charge Q a distance R away has magnitude E. In order to double the magnitude of the field at P, you could
double the charge to 2Q.
The current produced by voltage in a circuit is impeded by
electric resistance.
In an electrically neutral atom the number of protons in the nucleus is equal to the number of
electrons that surround the nucleus.
A device that transforms mechanical energy into electrical energy is a
generator
If the length and diameter of a wire of circular cross section are both doubled, the resistance is
halved.
If you thrust a magnet into a closed loop of wire, the loop will
have a current in it.
If you break a bar magnet in half you'll
have two magnets.
The frequency of induced voltage in a wire coil depends on
how frequently a magnet dips in and out of the coil
If you drop a bar magnet in a vertical copper pipe it will fall slowly because
it induces a magnetic field in the pipe that resists motion of the magnet.