Physics 2
The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 μT. What is the magnetic field at a distance of 4 cm from this wire?
2 μT
The primary of an ideal transformer has 100 turns and its secondary has 200 turns. If the input voltage to the primary is 100 V, we can expect the output voltage of the secondary to be
200 V (always inverse)
The current flowing through a circuit is changing at a rate of 3.00 A/s. If the circuit contains a 780.0 H inductor, what is the emf across the inductor?
2340 V
A charged particle is observed traveling in a circular path of radius R in a uniform magnetic field. If the particle were traveling twice as fast, the radius of the circular path would be
2R
While a magnet is moved toward the end of a solenoid (as shown in Figure 21.20), a voltage difference is induced between the two ends of the solenoid wire. The voltage difference would be larger if
All of the above statements are true.
A 5 H inductor carries a current of 2 amps. How can a self-induced EMF of 50 volts be made to appear across the inductor?
Change the current at the rate of 10 amps/sec.
A positive charge is moving to the right and experiences an upward magnetic force, as shown in the figure. In which direction must the magnetic field have a component.
Into the page
In Figure 21.17, a bar is in contact with a pair of parallel rails. A steady, uniform, magnetic field B is present. The bar is in motion with velocity ν. The polarity of the induced emf in terminals X and Y is:
X and Y are at the same potential
When a change of magnetic field occurs in a closed loop of wire,
all of the above
A transformer requires
alternating voltage.
The energy source for a generator may be
any of these
Like kinds of magnetic poles repel while unlike kinds of magnetic poles
attract
A magnetic field easily penetrates
both (human flesh and plastic coatings)
An electric generator of itself
cannot produce energy, but convert energy of other forms to electric energy.
Magnetic field lines about a current-carrying wire
circle the wire in closed loops.
A single current-carrying circular loop of radius R is placed next to a long, straight wire, as shown in the figure. The current I in the wire flows to the right. In which direction must current flow in the loop to produce a net magnetic field of zero at its center?
clockwise
If the bar magnet is kept fixed while the ring is dropped, what is the direction of the current induced in the ring, as viewed from below the ring
clockwise
A straight bar magnet is initially 4 cm long, with the north pole on the right and the south pole on the left. If you cut the magnet in half, the right half will
contain a north pole on the right and a south pole on the left.
When the switch is closed in the circuit, which way will the wire between the poles of the horseshoe magnet initially deflect.
downward
Which force field can increase a moving electron's speed?
electric field
Faradayʹs law is the law that describes
electromagnetic induction
Metal detectors that locate metal beneath sand on a beach are activated by
electromagnetic induction.
Compared to the huge force that attracts an iron tack to a strong magnet, the force that the tack exerts on the magnet is
equally huge
In Figure 21.6, a bar magnet moves away from the solenoid. The induced current through the resistor R is:
from a to b
n Figure 21.9, two parallel wires carry a current I in opposite directions. A rectangular loop is midway between the wires. The current I is decreasing. The induced current through the resistor R is:
from a to b
In Figure 21.15, a straight wire carries a current I. The wire passes through the center of a toroidal coil. The current is quickly reduced to zero. The induced current through the resistor R is:
from b to a
In Figure 21.8, one end of a bar is in contact with a circular rail and the other end is pivoted at P. A steady, uniform, magnetic field B is present. The bar rotates about P. The induced current through the resistor R is:
from b to a
Two solenoids are side by side. The switch S, initially open, is closed. The induced current through the resistor R is
from b to a?
Alternating current is normally produced by a
generator.
Compared to a motor, a generator is
its opposite.
A charged particle moving within a static magnetic field
may experience a magnetic force, but its speed will not change.
A device that transforms electrical energy to mechanical energy is a
motor
The source of all magnetism is
moving electric charge
An electron is moving to the right, as shown in the figure. Suddenly it encounters uniform magnetic field pointing out of the page. Which one of the three paths shown will it follow in the field?
path a
A rectangular coil, with corners labeled ABCD, has length L and width w. It is placed between the poles of a magnet, as shown in the figure. If there is a current I flowing through this coil in the direction shown, what is the direction of the force acting on section CD of this coil?
perpendicular to and out of the page
Maximum magnetic force occurs when electrons move
perpendicular to the magnetic field direction.
A negatively charged particle -Q is moving to the right, directly above a wire having a current I flowing to the right, as shown in the figure. In what direction is the magnetic force exerted on the particle due to the current?
upward