PHY Chapter 14 Smartbook
You have three identical magnets, A, B, and C, falling from the same height. Magnet A is falling through an incomplete copper ring. Magnet B is falling through a complete copper ring. Magnet C is falling through a coil of many turns. Rank the magnets according to the time it takes to reach the floor, with the longest time at the top.
1. C 2. B 3. A
If two parallel wires each 2.0-m long and separated by 1.0-m were each carrying 1.0 A of current, the force between them would be _____ x 10-7 N.
4 or four
A coil wire with 60 turns is placed in a magnetic field of 1 T. If the area of the coil is 0.06 m2 and the flux changes to zero in 0.5 s, the induced voltage is _____V according to Faraday's law.
7.2
Three identical rings, A, B, and C, are moving horizontally with the same speed. Ring A is moving in air without experiencing any magnetic field. Ring B is moving parallel to a horizontal magnetic field B. Ring C is moving perpendicular to and cutting through a magnetic field B. According to Faraday's law, an induced current will not flow in the following ring(s):
A B
Which of the following is an application of a current-carrying wire placed in a magnetic field?
An ammeter An electric motor
According to the figure, the pointer of the galvanometer does not deflect unless the current is _____.
Blank 1: alternating or changing
Near your home, a step down transformer is operating on the utility pole. When the voltage is stepped down, the _____ increases.
Blank 1: current, amps, or amperes
When a compass is placed near a current-carrying wire, it will _____. This indicates the presence of a _____ field around the wire.
Blank 1: deflect or move Blank 2: magnetic
If a current carrying conductor is placed in a magnetic field, it will experience a _____. This idea is the principle idea of _____.
Blank 1: force Blank 2: electromagnets
When the plane of the coil in a simple electrical generator is parallel to the external magnetic field, the induced voltage at this moment is _____ and the magnetic flux is _____.
Blank 1: maximum or maximized Blank 2: 0 or zero
An electric generator is a device to transform _____ energy into _____ energy.
Blank 1: mechanical Blank 2: electrical
There are no magnetic _____, but there are electric _____.
Blank 1: monopoles Blank 2: dipoles
The magnetic field lines emerge from the _____ pole and go into the _____ pole. In the case of an electric dipole, the electric field lines originate from the _____ pole and end on the _____ pole.
Blank 1: north Blank 2: south Blank 3: positive or + Blank 4: negative or -
Like poles _____ and unlike poles _____
Blank 1: repel Blank 2: attract
The magnetic force between two parallel current carrying wires is _____ when the currents flow in opposite directions and _____ when the currents flow in the same direction.
Blank 1: repulsive, repellent, or repel Blank 2: attractive or attract
The magnetic force acting on a positive charge moving parallel to the magnetic field equals ______ , and the force acting on a negative charge moving parallel to the magnetic field equals _____.
Blank 1: zero, 0, none, or nothing Blank 2: zero, 0, none, or nothing
Which of the following statements are true for the similarities between the magnetic and electric force? (Check all that apply.)
Both magnetic and electric forces are inversely proportional to the square of the distance Both magnetic and electric forces can be attractive or repulsive Both magnetic and electric forces can have dipoles
Two current carrying parallel wires are exerting a force of 5 N on each other. Which of the following changes would not change the force between them?
Cut the length in half and reduce the separation by half. Double the length and cut one current in half.
True or false: The magnetic flux is independent of the direction of the loop and magnetic field.
False
Which of the following are properties of an inductor?
Inductors have a back voltage that opposes changes in the current. Inductors have an effective electrical inertia.
Which are valid reasons for using the spring in the electromagnet shown in the figure?
It returns the pointer to the zero position when there is no current. It limits the movement of the pointer. Picture: https://tinyurl.com/yckv28b4
A coil of wire with 100 turns enters a constant magnetic field perpendicular to the plane of the coil, moves through it, and then exits. If the coil is connected to an ammeter, when and where do you expect the meter to deflect?
It will deflect as the coil exits the magnetic field. It will deflect at the as the coil enters the magnetic field.
Magnetic field strength is measured in teslas (T). Another way to express this unit is as _____.
N/A⋅m
Which of the following statements are true for the unit of current?
The ampere is the basic unit of electromagnetism. The ampere is the force exerted between two current-carrying wires. The coulomb is defined from the ampere.
According to the figure, what will happen when the plane of the coil is perpendicular to the magnetic field?
The coil will stop. Picture: https://tinyurl.com/bdhv35nx
Suppose equal positive and negative charges are moving with the same velocity in the same magnetic field. Which of the following statement is correct regarding the directions of the magnetic forces acting on the charges?
The directions of the magnetic forces acting on the charges are opposite.
Which of the following statements are true for the force between the poles of two magnets?
The force follows a similar relationship as that of Coulomb's law for electric charges. The force decreases as the inverse of the square of the distance between the poles.
Choose the correct statements about the magnetic force acting on a charge moving in a magnetic field.
The force is directly proportional to the amount of charge. The force is directly proportional to the strength of the magnetic field.
Match the following pairs to form complete sentences.
The magnetic field lines around a current-carrying wire are in the shape of - concentric circles. The right-hand rule states that the thumb points - in the direction of the current. The direction of the magnetic field around a current-carrying wire is - perpendicular to the current. The right-hand rule states that the fingers curl around the wire in the direction of - the magnetic field.
Which of the following statements are true for the magnetic flux through a loop?
The magnetic flux is proportional to the magnitude of the magnetic field. The magnetic flux is proportional to the area bounded by the loop.
Which of the following is the correct statement about the magnetic force between two magnets?
The magnetic force between two magnets is inversely proportional to the square of the distance between them.
Which of the following is true about the magnetic force on a moving charge?
The magnetic force causes a centripetal acceleration. The magnetic force does not do any work on electric charges.
Which of the following statements are correct about the magnetic force per unit length between two identical, parallel, current carrying wires.
The magnetic force per unit length is directly proportional to the length of the wires. The magnetic force per unit length is inversely proportional to the distance between the wires. The magnetic force per unit length is directly proportional to the currents.
Which of the following statements are true for a compass showing directions?
The north pole of the compass points towards the approximate geographic north of the Earth. The north pole of the compass points towards the magnetic south pole of the Earth.
Match the following pairs based on their function shown in the figure. Instructions
The spring ----- controls the movement of the pointer. The iron core ----- strengthens the magnetic field. The magnet ----- provides the external magnetic field. The pointer ----- deflects with the coil to indicate the current. Picture: https://tinyurl.com/yckv28b4
Match the following pairs based on the right-hand rule for the magnetic force on a moving charge.
The thumb ----- indicates the magnetic force. The index finger ----- indicates the direction of the velocity of the moving charge. The middle finger ----- indicates the direction of the magnetic field.
True or false: An alternating or changing current in the primary coil is a prerequisite for the transformer to work.
True
In the setup shown in the figure, a momentary deflection is observed by the galvanometer at the moment the circuit is flipped off and on again. Which of the following are the reasons for the deflection?
When the current reaches its constant value, there is no more induction. The moment the circuit is closed, the magnetic field changes from zero to some value. The moment the circuit is opened, the magnetic field changes from a nonzero value to zero. Picture: https://tinyurl.com/d734zf9m
When will the torque from a magnetic field on a current carrying loop be equal to zero?
When the plane of the loop is perpendicular to the magnetic field.
All of the following can be attracted to a magnet except
a copper wire.
On a utility pole near your home, the transformer is
a step down transformer.
According to the figure, F1 and F2 produce no torque because they are
acting in opposite direction along the same line of action.
The shape of the magnetic field lines produced by making a loop of current comes from the magnetic fields of each little piece of the current _____ together.
adding or accumulated
To keep the current-carrying coil turning in a magnetic field, as shown in the figure, a(n) _____ current must be used.
alternating or AC Picture: https://tinyurl.com/bdhv35nx
The current produced from a simple electrical generator is
alternating, changing, or AC
A current-carrying circular loop is considered a dipole because the shape of the magnetic field lines around it is similar to that of a _____ magnet.
bar
When a current-carrying wire is bent into a circular loop, the magnetic fields produced by different segments of the wire add to give a strong field at the _____ of the loop.
center
Inductors in circuits can smooth out _____ in the current.
changes
If the distance between two magnets is doubled, the force between them will
decrease to one-fourth of the original force.
If you wanted to increase the magnetic flux through a loop to nine times its original value, you could
increase the magnetic field to nine times its original strength. triple the radius of the loop.
If the coil in the figure is wound around an iron core, its ability to attract iron filings placed near it will
increase. Picture: https://tinyurl.com/2p8pvf2v
We can investigate the magnetic field lines by sprinkling _____ filings on a paper covering the magnet.
iron, ferromagnetic, or Fe
Factors affecting the strength of the magnetic field near the axis of the coil shown in the figure include the
magnitude of the current. number of turns. coil length. Picture: https://tinyurl.com/2p8pvf2v
Electrical companies send electricity in power lines with high voltage and low current in order to
minimize the power that is lost in the form of heat.
We can imagine that inside the Earth there is a magnet whose south pole is directed close to the geographic ______.
north Picture: https://tinyurl.com/2sdyft6y
The magnetic flux is the _____ of magnetic field lines passing through a loop.
number
If the rate of change of the original flux increases, the induced magnetic field will be in the _____ direction compared to the original field.
opposite, opposing, or negative
The magnetic force does no work on electric charges because it is _____ to the motion of the charge.
perpendicular
A stationary charge is placed in a magnetic field. If both the magnetic filed and the charge are doubled, then the magnetic force on the charge will
remain constant and equal to zero.
Magnetic forces can be attractive or ______
repulsive or repellent
If the number of coils in the secondary coil of a transformer is larger than that of the primary coil, the voltage will
step up.
The magnetic field lines at the center of a current-carrying circular loop are in the shape of _____ lines.
straight
Lenz's law defines
the direction of the induced current in a conductor experiencing a changing magnetic flux.
The direction of the magnetic force acting on a charge moving in a magnetic field is perpendicular to
the direction of the magnetic field. the velocity of the charged particle.
According to the figure, when the battery supplies a steady current, no deflection in the galvanometer is observed. This is because
the magnetic field is not changing. Picture: https://tinyurl.com/d734zf9m
According to the figure, F3 and F4 produce a torque because
there is a separation between their lines of action Picture: https://tinyurl.com/2p8dy5fh
A positive charge is moving from left to right in a magnetic field directed into the page. The direction of the magnetic force acting on this charge is _____.
upward
A transformer is a device used to change the
voltage
If the coil as shown in the figure is wound around an iron core, its ability to attract iron filings is ___.
will increase
A coil wire with 60 turns and a cross-sectional area of 0.02 m2 is placed in a constant magnetic field of 1 T. According to Faraday's law, the induced voltage is _____V.
zero or 0
