Phys test 2
When the magnetic dipole moment (as defined by the right hand rule) is in the same direction as the magnetic field.
A DC Motor consists of a stationary magnetic field and a wire loop with a commutator that can switch the direction of the current in the loop. At what point in the rotation should the current switch directions?
no
A circular loop of conducting wire is moving through a uniform magnetic field, as shown in (Figure 2). Is a non-zero emf induced in the loop?
an induced current flows counterclockwise in the loop of wire
A circular loop of wire lies flat on a level table top in a region where the magnetic field vector points straight upward. The magnetic field suddenly vanishes. As viewed from above, in what direction does the induced current flow in the loop of wire?
No current is induced in the loop of wire
A circular loop of wire lies flat on a level table top. A bar magnet is held stationary above the circular loop with its north pole point downward. As viewed from above, in what direction does the induced current flow in the loop of wire?
The induced current flows through the bulb from the left to the right
A conducting rod is being dragged along conducting rails, as shown in (Figure 1). The magnetic field is directed out of the screen. In what direction does the induced current flow through the light bulb?
Toward the west
A long straight vertical wire carries a current straight down. At a point due south of this wire, the magnetic field points
(0,6*10^-11,0)T
A long, straight wire lies along the z-axis and carries a 4.00 AA current in the +z-direction. Find the magnetic field produced at the point x= 2.00m, y = 0, z = 0 by a 0.600 mm segment of the wire centered at the origin.
Toward the north
A vertical wire carries a current vertically upward in a region where the magnetic field vector points toward the east. What is the direction of the magnetic force on this current due to the field?
points straight up.
A wire formed into a circular loop lies flat on a table top and carrys a current. When viewed from above, the current moves around the loop in a counterclockwise sense. For points INSIDE the loop, the magnetic field caused by this current
m/q = R^2(B_0^2)/2V
After being accelerated, the particle enters a uniform magnetic field of strength B0�0 and travels in a circle of radius R� (determined by observing where it hits on a screen--as shown in the figure). The results of this experiment allow one to find m/q�/� in terms of the experimentally measured quantities such as the particle radius, the magnetic field, and the applied voltage.What is m/q/? Express m/q/ in terms of B0, V, R, and any necessary constants.
true
Ampère's law can be used to analytically find the magnetic field around a straight current-carrying wire
false
Ampère's law can be used to analytically find the magnetic field at the center of a circle formed by a current-carrying conductor.
false
Ampère's law can be used to analytically find the magnetic field at the center of a square loop carrying a constant current.
true
Ampère's law can be used to analytically find the magnetic field inside a toroid. (A toroid is a doughnut shape wound uniformly with many turns of wire.
g) the electron moves with constant speed in a counter-clockwise circle completing a revolution every 4.77 × 10−11 s.
An electron has an initial velocity to the right (+x) in a region of uniform magnetic field of 0.75 T directed out of the page (+z) toward the viewer. Which of the following describes the electrons motion? (mel = 9.11 × 10−31 kg, q = − 1.60 × 10−19 C) a) the electron moves with constant speed in a clockwise circle completing a revolution every 2.10 × 1010 s. B) the electron moves with constant speed in a counter-clockwise circle completing a revolution every 2.10 × 1010 s. C) the electron moves in a straight path at a constant velocity D) the electron moves in a straight path and accelerates at 2.10 × 1010 E) the electron moves with constant speed in a clockwise circle completing a revolution every 4.77 × 10−11 s. f) the electron moves in a straight path and accelerates at 4.77 × 10−11 g) the electron moves with constant speed in a counter-clockwise circle completing a revolution every 4.77 × 10−1
-Y direction
At a given moment the particle is moving in the +x direction (and the magnetic field is always in the +z direction). If q is positive, what is the direction of the force on the particle due to the magnetic field?
A, B, D
At the same temperature, two wires made of pure copper have different resistances. The same voltage is applied at the ends of each wire. The wires may differ in a)length. b) cross-sectional area c) resistivity d) amount of electric current passing through them.
338mA
Calculate the current through a 10.0-m long 22 gauge (having radius 0.321 mm) nichrome wire if it is connected to a 12.0-V battery. The resistivity of nichrome is 100 × 10−8 Ω • m. A) 17.5A b) 776mA c) 61.8 A d) 30.9 A e) 338mA
U_0I/4R into the page
Calculate the magnitude of the magnetic field at point P due to the current in the semicircular section of wire shown in the figure (Figure 1). (Hint: Does the current in the long, straight section of the wire produce any field at P?) answer in terms of I, R, and U_0 Find the direction of the magnitude at point P
U_0I^2/4pid
Calculate the magnitude of the net magnetic force per unit length on the bottom wire. Express your answer in terms of I, d, and magnetic constant μ0. what is its direction
0
Calculate the magnitude of the net magnetic force per unit length on the middle wire. Express your answer in terms of I, d, and magnetic constant μ0.
C>B=A>E=F
Consider a circuit containing five identical light bulbs and an ideal battery. Assume that the resistance of each light bulb remains constant. Rank the bulbs (A through E) based on their brightness.
circuit B
Consider circuitsA, B, and C which are all made of identical voltage sources, V, and resistors, R. In which of the three circuits is the power provided by the voltage source the greatest?
I1>I2 and E1>E2
Consider two cylindrical resistors: R1�1 and R2�2, which are made of the same material and have the same cross sectional area, but R2�2 has a length that is greater than that of R1�1. The two resistors are connected in parallel and attached to a voltage source to create a complete circuit. What is the relationship between the currents in the two resistors I1�1and I2�2 AND the electric fields in the two resistors, E1�1 and E2�2?
U_s = (deltaV/R)B_0L)/mg
Find U_s the coefficient of static friction between the rod and rails
out of the page
Find the direction of the magnetic field that the electron produces at the location of the nucleus (treated as a point).
(0,0,0)T
Find the magnetic field produced at the point x = 0, y= 0, z= = 2.00 mm by a 0.600 mmmm segment of the wire centered at the origin.
(-2.12*10^-11, 2.12*10^-11, 0)T
Find the magnetic field produced at the point x = 2.00 mm, y = 2.00 mm, z = 0 by a 0.600 mm segment of the wire centered at the origin.
(-6*10^-11,0,0)
Find the magnetic field produced at the point x= 0, y = 2.00 mm, z =0 by a 0.600 mmmm segment of the wire centered at the origin. Enter your answers numerically separated by commas.
B=13T
Find the magnitude of the magnetic field that the electron produces at the location of the nucleus (treated as a point)
C) Between points K and M
For the circuit shown on the left in (Figure 1), which potential difference corresponds to the terminal voltage of the battery? A) between points K and L B) Between points L and M C) Between points K and M
c) The thicker wire has one-fourth the resistance of the thinner wire.
How do the resistances of two conducting wires compare if they have the same length, but one is twice the radius of the other? a) The resistance is the same in both wires. b) The thicker wire has half the resistance of the thinner wire. c) The thicker wire has one-fourth the resistance of the thinner wire. d) The thicker wire has twice the resistance of the thinner wire. Submit
W = 360J
How much work W does the battery connected to the 21.0-ohm resistor perform in one minute?
No reading. The ammeter is connected incorrectly and has a very low internal resistance. Therefore, the current would be dangerously high and might damage the battery or ammeter.
If a circuit was constructed according to this circuit diagram. What would the ammeter read?
3.21 kg
If the maximum terminal voltage of the battery is 175 VV, what is the greatest mass m� that this instrument can measure?
The voltage is reduced by a factor of 2.
If the resistance in a circuit connected to a constant current is halved, how is the voltage in the circuit affected?
c) Electrons in gold are more likely to be scattered than electrons in copper at room temperature when they are accelerated by the same electric field.
If the resistivity of copper is less than that of gold at room temperature, which of the following statements must be true? a) Gold has a higher resistance than copper. b) The sample of gold is thinner than the sample of copper. c) Electrons in gold are more likely to be scattered than electrons in copper at room temperature when they are accelerated by the same electric field. d) There is more current flowing in the gold than in the copper. Submit
ω = qB_0/m
If the resulting trajectory of the charged particle is a circle, what is ω, the angular frequency of the circular motion? Express ω in terms of q, m, and B_0.
twice as great
If the speed of the magnet is doubled, the induced voltage is
The current is Doubled
If the voltage across a circuit of constant resistance is doubled, how is the current in the circuit affected?
E = 5.1*10^11 N/C Toward the electron
In the Bohr model of the hydrogen atom, the electron moves in a circular orbit of radius 5.3×10−11m5.3×10−11m with a speed of 2.2×106m/s2.2×106m/s. If we are viewing the atom in such a way that the electron's orbit is in the plane of the paper with the electron moving clockwise, find the magnitude of the electric field that the electron produces at the location of the nucleus (treated as a point). Express your answer in newtons per coulomb. Find the direction of the electric field that the electron produces at the location of the nucleus (treated as a point).
2*10^-7 N/m
In the SI system, the unit of current, the ampere, is defined by this relationship using an apparatus called an Ampère balance. What would be the force per unit length of two infinitely long wires, separated by a distance 1m, if 1A of current were flowing through each of them? Express your answer numerically in newtons per meter.
A, B, C, D
In the figure, a conducting rod is shown moving in a uniform magnetic field . Which of the following statements are true? A) The free charges in the rod are acted upon by a magnetic force. B)The magnitude of the potential difference in the rod is proportional to the velocity v of the rod. C)The magnitude of the potential difference in the rod is proportional to the strength of the magnetic field. D) An electric field is established in the rod directed from point a to point b. E) The magnitude of the potential difference in the rod is inversely proportional to the length L of the rod.
I = .5A
In the situation described in Part I, what is the current I through the 21.0-ohm resistor?
C
In which diagram does the voltmeter correctly measure the terminal voltage of the battery? Choose the best answer.
D
In which diagram does the voltmeter read almost zero?
A
In which diagram is the current through the battery nearly zero?
C and D
In which diagram or diagrams does the ammeter correctly measure the current through the resistor with resistance R?
A and B
In which diagram or diagrams does the ammeter read almost zero?
C and D
In which diagram(s) (labeled A - D) is the ammeter connected correctly to measure the current through the battery? A B C D
A>B>C=E
Now assume that particles A, B, C, and E all have the same magnitude of electric charge. Rank the particles A, B, C, and E on the basis of their speed. Rank from largest to smallest. To rank items as equivalent, overlap them.
U_0I^2/4pid upward direction
Part complete Calculate the magnitude of the net magnetic force per unit length on the top wire. Express your answer in terms of I, d, and magnetic constant μ0. What is its direction
8.0 Ω
Part complete Thirteen resistors are connected across points A and B as shown in the figure. If all the resistors are accurate to 2 significant figures, what is the equivalent resistance between points A and B? a) 4 b) 6 c) 10 d) 12 e) 8
the picrtue is the right answer
Rank the orientations from lowest to highest magnitude of the instantaneous induced emf.
The correct ranking cannot be determined.
Rank the particals on their speed.
12V
Refers to battery with EMF of 12 v and internal resistance of 3 ohms. A voltmeter is connected to the terminals of the battery; the battery is not connected to any other external circuit elements. What is the reading of the voltmete?
A and B
The Hall Effect can be used to: A) determine whether the charge carriers in a material are positive or negative. B)determine the concentration of charge carriers in a material. C)explain superconductivity with mutual attraction of electrons into Cooper pairs. D) explain superconductivity by metaphor with a charged particle moving down an oppositely charged hallway.
along any closed path you choose
The circle on the integral means that Br must be integrated
4<-
The diagram shows only a small section of a circuit. Current is flowing into and out of this section as shown by the arrows. For example, 3 A of current is flowing into the left side of R1 from the left hand wire. What is the magnitude and direction of the current flowing in or out of the right hand wire, labelled "i" in the diagram?
remain constant
The fact that the magnetic field generates a force perpendicular to the instantaneous velocity of the particle has implications for the work that the field does on the particle. As a consequence, if only the magnetic field acts on the particle, its kinetic energy will ____________.
the line integral along the closed loop.
The integral on the left is
F = (U_0I_2m)/ 2pi(d^2-a^2/4)
The magnetic moment m⃗ �→ of a current loop is defined as the vector whose magnitude equals the area of the loop times the magnitude of the current flowing in it (m=IA�=��), and whose direction is perpendicular to the plane in which the current flows. Find the magnitude, F�, of the force on the loop from Part A in terms of the magnitude of its magnetic moment. Express F� in terms of m�, I2�2, a�, d�, and μ0�0.
At twice the distance, the magnitude of the field is B/2.
The magnitude of the magnetic field at a certain distance from a long, straight conductor is represented by B. What is the magnitude of the magnetic field at twice the distance from the conductor?
unchanged
The same magnet is plunged into a coil that has twice the number of turns as before, making it twice as long. The magnet is shown before it enters the coil in (Figure 2). If the speed of the magnet is again v�, the induced current in the coil is _______ .
I = .5 A
The voltmeter is now removed and a 21.0-ohm resistor is connected to the terminals of the battery. What is the current I through the battery?
remain perpendicular to the direction of motion
This force will cause the path of the particle to curve. Therefore, at a later time, the direction of the force will ____________.
1 is negative, 2 is neutral, and 3 is positive.
Three particles travel through a region of space where the magnetic field is out of the page, as shown in the figure. The electric charge of each of the three particles is, respectively,
B and D
Two long parallel wires are placed side by side on a horizontal table. The wires carry equal currents in the same direction. Which of the following statements are true? A) The magnetic force between the two wires is repulsive. B) The magnetic field at a point midway between the two wires is zero. C) The magnetic field is a maximum at a point midway between the two wires. D) The magnetic force between the two wires is attractive. Submit
The emf around the two wire loops is the same and is non-zero.
Two loops of wire, each having a different radius, encircle an infinitely long solenoid, as shown in (Figure 3). The magnetic field B⃗ �→ is zero outside the solenoid. The current through the solenoid is increasing with time, causing the magnetic field inside the solenoid to increase with time. Which statement is true?
Bulb A gets dimmer. Bulb C gets brighter
What happens to brightness of bulb A? What happens to bulb C?
BA→A is out of the page.
What is the direction of the magnetic field BA→A at Point A?
Bb is onto the page
What is the direction of the magnetic field BB→ at Point B?
Bc is out of the page
What is the direction of the magnetic field Bc at Point C?
Bd is out of the page
What is the direction of the magnetic field Bd and point D
Be is onto the page
What is the direction of the magnetic field Be at point E
Bnet points out of the screen at point A
What is the direction of the magnetic field Bnet at point A?
Bnet = 0 at B
What is the direction of the magnetic field Bnet at point B?
Bnet points onto the screen at C
What is the direction of the magnetic field Bnet at point C?
the unit vector pointss from point charge where field is measured from the proton to point P Bright = 0T Bleft = 0T B = 1.21*10^-12T Out of the page The magnitude of the magnetic field would be the same but the direction would be reversed.
What is the direction of the unit vector R in the equation What is the magnitude of the magnetic field caused by this proton if it is moving to the right? What is the magnitude of the magnetic field caused by this proton if it is moving to the left? What is the magnitude of the magnetic field caused by this proton if it is moving toward the top of the page? What is the direction of the magnetic field caused by this proton if it is moving toward the top of the page? What is the answer to parts D and E for an electron instead of a proton?
(U_0 I_1 I_2 a^2) 2pi(d^2-a^2/4)
What is the magnitude F of the net force on the loop? Express the force in terms of I1, I2, a, d, and μ0.
B= 1.2 T East
What is the magnitude of the minimum magnetic field that will keep the particle moving in the earth's gravitational field in the same horizontal, northward direction? What is the direction of the minimum magnetic field?
1.03X10^-2 T +z direction
What is the magnitude of the uniform magnetic field in the region, if the proton is to pass through undeflected? Assume that the magnetic field has no x-component and neglect gravitational effects. a) 1.65 × 10^−21 T b) 6.99 × 10^10 T C) 97.3 T D) 1.56 × 10^−17 T E) 1.03 × 10^−2 T What is the direction of this uniform magnetic field?
ΔV = 10.5 V
What is the potential difference ΔV across the 21.0-ohm resistor from Part I?
ΔV = 10.5 V
What is the terminal voltage ΔV of the battery connected to the 21.0-ohm resistor from Part I?
The net current through the loop
What physical quantity does the symbol Iencl represent?
A and B
Which of the following choices of path allow u to use ampere law to analytically find B(r) a) the path must pass through point r b) the path must have enough symmetry so the B(r) * dl is constant along large parts of it c) the path must be a circle
A, C, D, E
Which of the following statements are true concerning electromagnetic induction? A) It is possible to induce a current in a closed loop of wire by changing the strength of a magnetic field enclosed by the wire. B) It is possible to induce a current in a closed loop of wire remaining at rest and located in a uniform magnetic field. C) It is possible to induce a current in a closed loop of wire by change the orientation of a magnetic field enclosed by the wire. D) It is possible to induce a current in a closed loop of wire without the aid of a power supply or battery. E) It is possible to induce a current in a closed loop of wire located in a uniform magnetic field by either increasing or decreasing the area enclosed by the loop. Submit
A, B, D
Which of the following statements are true concerning the creation of magnetic fields? A) A permanent magnet creates a magnetic field at all points in the surrounding region. B) An electric current in a conductor creates a magnetic field at all points in the surrounding region. C) A single stationary electric charge creates a magnetic field at all points in the surrounding region. D) A moving electric charge creates a magnetic field at all points in the surrounding region. E) A distribution of electric charges at rest creates a magnetic field at all points in the surrounding region.
C, D, E
Which of the following statements are true concerning the creation of magnetic fields? a) A distribution of electric charges at rest creates a magnetic field at all points in the surrounding region. B) A single stationary electric charge creates a magnetic field at all points in the surrounding region. C) An electric current in a conductor creates a magnetic field at all points in the surrounding region. D) A permanent magnet creates a magnetic field at all points in the surrounding region. E) A moving electric charge creates a magnetic field at all points in the surrounding region.
A and B
Which of the following statements are true? a)In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges B) Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time. C) When an electric field is applied to a conductor, the free electrons move only in the direction opposite the applied electric field. D)In a circuit, current is delivered by the positive terminal of a battery, and it is used up by the time it returns to the negative terminal of the battery. C)By convention, the direction of a current is taken to be the direction of flow for negative charges.
B, D, F
Which of the following will increase the resistance of a wire? A) Increasing the cross-sectional area of the wire will increase the resistance of the wire. B) Increasing the length of the wire will increase the resistance of the wire. C) Decreasing the resistivity of the material the wire is composed of will increase the resistance of the wire. D) Increasing the resistivity of the material the wire is composed of will increase the resistance of the wire. E) Decreasing the length of the wire will increase the resistance of the wire. F) Decreasing the cross-sectional area of the wire will increase the resistance of the wire.
c) Double the voltage across it.
Which of the following would double the amount of current flowing through a piece of metal wire? a) Quarter the voltage across it. b) Halve the voltage across it. c) Double the voltage across it. d) Quadruple the voltage across it. Submit
Partical A
Which particle (if any) is negatively charged?
Partical D
Which particle if any are neutral
a
Which point, a or b, should be the positive terminal of the battery?
u = sqrt (2qV)/m
With what speed u does the ion exit the acceleration region? Find the speed in terms of m, q, V, and any constants
wire of length L and area 2A > wire of length L and area A > wire of length 2L and area A.
You are given three pieces of wire that have different shapes (dimensions). You connect each piece of wire separately to a battery. The first piece has a length L and cross-sectional area A. The second is twice as long as the first, but has the same thickness. The third is the same length as the first, but has twice the cross-sectional area. Rank the wires in order of which carries the most current (has the lowest resistance) when connected to batteries with the same voltage difference.
attractive F/L = (U_0I^2)/2pid
You are given two infinite, parallel wires each carrying current I�. The wires are separated by a distance d�, and the current in the two wires is flowing in the same direction. This problem concerns the force per unit length between the wires. Is the force between the wires attractive or repulsive? What is the force per unit length F/L/ between the two wires? Express your answer in terms of I, d, and constants such as μ0 and π.
e) 2.1A
see picture a) 1.6 A B) 2.7A c) 1.9A d)2.4A e) 2.1A
