Physics 2 PLV + HW

1.1 A compass is placed in a magnetic field, and the compass needle is oriented as shown in the figure (up). What is the direction of the magnetic field at the location of the compass? Down Up Right Left

up

Which one of the following is a good conductor? Glass Wood Cloth Lead

lead

3.2 The figure shows three particles with identical charge magnitudes and masses moving through a uniform magnetic field inside a bubble chamber. Which particle has the greatest speed?

**confused 3 as the radius is given as R = m * v/(B * q ) for identical mass and charge , the particle with greatest speed will have largest radius hence ,the particle 3 has the greatest speed

Suppose a charge of -6 q is suspended inside a cavity in an electrically neutral cylindrical conductor. What is the charge induced on the interior surface? +6q +3q -6q -3q

+6q

Suppose a charge of +6 is suspended inside a cavity in an electrically neutral cylindrical conductor. What is the charge induced on the exterior surface? +3q -3q +6q -6q

-6q

5.1 A current carrying wire is experiencing a magnetic force in a magnetic field. What happens to the direction of the magnetic force on the wire, if the current in the wire is reversed? -The magnitude of the forces decreases, but it remains in the same direction. -The magnitude of the force remains unchanged, but it is oriented perpendicular to the direction of the original force. -The magnitude of the force remains unchanged, but it reverses direction. -Nothing. The magnitude and direction of the force remain unchanged.

-The magnitude of the force remains unchanged, but it reverses direction. Right-hand-rule #1 gives the direction of the force on a current-carrying wire, and it does depend on the direction of the current.

7.2 Resistors 22 Ω and 47 Ω are wired in parallel with a battery of voltage 12.0 V. is now replaced by a wire. What is the current through ? 0.23 A 0.55 A 0 A 3.1 A

0A if one of the resistors is replaced by a wire, that is considered a "short" in the circuit. All of the current will bypass the remaining resistor and go through the short.

4.1 A circuit is composed of a 12.0 V battery and a 110 Ω resistor. What is the power dissipated by the resistor? 1.3 W 0.11 A 1.3 A 0.11 W

1.3 W

9.1 A 12-V car battery has an internal resistance of 0.020 Ω. When the headlights and stereo are on, a current of 25.0 A is drawn from the battery. What is the value of the terminal voltage when this current is drawn from the battery? 12 V 12.5 V 9.0 V 11.5 V

11.5 V

5.1 The 110 V provided by common wall sockets in the United States is given as a root-mean-square (rms) voltage. What is the peak value of the voltage? 155 V 220 V 78.0 V 110 V

155V

2.2 The figure shows three identical charged particles moving with the same speed but at different directions in a uniform magnetic field. Rank the charges in order of the magnetic force each one experiences, starting with the largest. 1, 2, 3 3, 1, 2 2, 1, 3 3, 2, 1

2, 1, 3

Suppose the electric field of a point charge of +5q is represented by 20 field lines directed radially outward from the charge. How should the electric field of a point charge of -10 be represented? 40 field lines directed radially outward 10 field lines directed radially outward 40 field lines directed radially inward 10 field lines directed radially inward

40 field lines directed radially inward

1.2 Suppose that a current of 1.5 A is used to charge a conductor. After 4.0 s, how much charge is delivered to the conductor.

6.0 C

6.1 Which of the following would increase the torque on a current-carrying loop of wire placed in a magnetic field? Increase the number of turns in the loop. Increase the cross-sectional area of each loop. Increase the strength of the magnetic field. Rotate the loop so that the normal to the loop's surface is parallel to the magnetic field. All of the above.

All of the above.

6.1 Suppose a negative point charge is placed at x=0 and an electron is placed at some point on the positive x-axis. What is the direction of the electric field at point due to the point charge, and what is the direction of the force experienced by the electron due to that field? E along +x; along +x E along +x; along -x E along -x; along -x E along -x; along +x

E along -x; along +x (they're repelling)

1.2 Which of the following is/are true? I. The earth has a magnetic field. II. The earth's magnetic field is similar to a bar magnet. III. The north magnetic pole and geographic north are located at exactly the same point. IV. The earth's magnetic field is constant and never changes. I only I and II only III only All of the above.

I and II only

5. Each of two identical objects carries a net charge. The objects are made from conducting material. One of them is attracted to a positively charged ebonite rod, and the other is repelled by the rod. After the objects are touched together, it is found that they are each repelled by the rod. What can be concluded about the initial charges on the objects? Initially both objects are positive, with both charges having the same magnitude. Initially one object is positive and one is negative, with the positive charge having a greater magnitude than the negative charge. Initially one object is positive and one is negative, with the negative charge having a greater magnitude than the positive charge. Initially both objects are negative, with both charges having the same magnitude.

Initially one object is positive and one is negative, with the positive charge having a greater magnitude than the negative charge. The fact that the positive rod repels one object indicates that that object carries a net positive charge. The fact that the rod repels the other object indicates that that object carries a net negative charge. Since both objects are identical and made from conducting material, they share the combined net charges equally after they are touched together. Since the rod repels each object after they are touched, each object must then carry a net positive charge. But the net electric charge of any isolated system is conserved, so the total net charge initially must also have been positive. This means that the initial positive charge had the greater magnitude.

When you bring a negatively charged rod near a piece of electrically neutral plastic it attracts it. What happens if you instead bring a positively charged rod near the plastic? It attracts. It repels. There is no force between the rod and the plastic.

It attracts.

Suppose the resistor in an RC circuit is doubled in value. How should the value of the capacitance be changed in order to keep the same time constant? It should remain the same. It should be quadrupled. It should be halved. It should be doubled.

It should be halved.

12.2 For two identical capacitors of capacitance in a circuit containing a battery of voltage V , which configuration of the capacitors stores the most charge? Using only one of the capacitors. Series wiring of the two capacitors. They are all the same. Parallel wiring of the two capacitors.

Parallel wiring of the two capacitors.

2.2 Suppose that a current I flows through a single-loop circuit containing a battery (voltage V ) and a resistor (resistance R ). What parameter changes below would reduce the current to half of its original value?

Set resistance to 2 R

The electric potential is constant throughout a certain region of space. What can you say about the electric field in this region? The electric field is zero. The electric field is non-zero.

The electric field is zero.

A proton and electron are simultaneously released from rest at the midpoint between the plates of a charged parallel-plate capacitor. Which particle strikes one of the plates first? The electron. The proton. Both particles strike a plate at the same time.

The electron. The force on each particle due to the electric field between the plates will be equal. However, the acceleration of each particle will not be the same. **mass of electron is smaller than mass of proton

5.2

The force on a current-carrying wire is given by Equation 21.3 and depends on the angle between the current in the wire and the magnetic field.

6.1 Two identical resistors () are wired in series with a battery of voltage . Suppose one of the resistors is removed from the circuit. How does the power dissipation of the single resistor compare to the power dissipation of that resistor when the second resistor was in the circuit? The power dissipation is halved. The power dissipation is doubled. It is the same. The power dissipation is quadrupled.

The power dissipation is quadrupled. With two resistors in the circuit, half the voltage is across each resistor. The entire voltage is across the single resistor when the second one is removed. The battery voltage remains unchanged. Use P=V^2/R

2.1 A proton is released from rest at a location in space where the magnetic field points upward toward the top of the page. Which of the following is true? The proton experiences a magnetic force upward. The proton experiences no magnetic force and remains at rest. The proton experiences a magnetic force downward. The proton experiences a magnetic force to the right.

The proton experiences no magnetic force and remains at rest (bc it's not moving)

3.1 Two copper wires have the same length but different cross sectional areas. The cross-sectional area of wire 1 is A, and that of wire 2 is 2A. How are the resistances of the two wires related? The are the same. Wire 1 has four times the resistance of Wire 2 Wire 1 has half the resistance of Wire 2

Wire 1 has twice the resistance of Wire 2

1.1 If 2.0 C of charge passes through a wire in time 0.25 s, what is the current in the wire?

8.0 A

3.1 The potential at a distance from a positive point charge is +V. What is the potential at a distance of r/3? +3V +V +(1/3)V

+3V Recall that the potential of a point charge goes as . a)Consider q as the positive charge.V = kq/rWhere k = 1/4o When r becomes r/3,New potential, V' = kq/(r/3)= 3kq/r= + 3V

An electrically isolated object is electrically neutral. What is the charge on the object if you remove three electrons? +3e Zero -3e Impossible to tell

+3e

11.2 A circuit contains a 100-Ω resistor and a 48.0-V battery. An ammeter is inserted into the circuit to measure the current and has an internal resistance of 0.50 Ω. What is the voltage drop across the ammeter terminals? 0.24 V 47.8 V 5.00 V 0.50 V

0.24 V

2.1 A single-loop circuit consists of a 9.0 V battery and a 22 Ω resistor. How much current will flow in this circuit?

0.41 A

7.2 At a distance of 2.5 cm from a long straight current-carrying wire, the magnetic field has a value of 1.3 T. What would be the value of the magnetic field at a point that is twice as far from the wire, when the wire carries twice as much current?

1. 3T

8.1 You have three identical resistors that you can connect in various ways. Which of the following is NOT a possible value of the equivalent resistance of the three-resistor combinations R/3 3R 3R/2 4R

4R

11.1 A voltmeter has an internal resistance of 10 000 Ω and is used to measure the voltage across a 47.0-Ω resistor that, without the voltmeter connected, has a current of 1.20 A pass through it. How much current is drawn away from the circuit by the voltmeter when it is connected across the resistor? 4.7 mA 5.6 mA 1.205 A 0 A

5.6 mA

8.2 You have five identical resistors. How should they be wired in order to have the minimum possible effective resistance? All in parallel Three in series, two in parallel Two in series, three in parallel All in series

All in parallel

4.1 Which of the following is/are true? A mass spectrometer has many uses in both physics and chemistry. A mass spectrometer can be used to identify charged particles with different masses. A mass spectrometer takes advantage of the fact that charged particles are deflected into circular trajectories within a magnetic field. All of the above are true.

All of the above are true.

4.1 Which of the following statements is/are true? I. An equipotential surface is a surface of constant potential. II. The electrostatic force does no work on a charge that moves along an equipotential surface. III. The equipotential surfaces surrounding a point charge consist of an infinite number of concentric spherical shells. IV. Electric field lines are everywhere perpendicular to equipotential surfaces. I only I and II only III and IV only All of the above.

All of the above.

8.1 True or False: A piece of unmagnetized iron, with randomly oriented magnetic domains, would not be attracted to a permanent magnet. False True

False

8.2 True or False: An aluminum can could be picked up by an electromagnetic at a recycling center. True False

F

5.1 Which of the following would increase the capacitance of a parallel-plate capacitor? I. Insert a dielectric between the plates. II. Increase the surface area of each plate. III. Increase the separation distance between the plates. I and II only II and III only All of the above.

I and II only

2.1 Three points A, B, and C are located along a horizontal line, as the figure shows. A positive charge is released from rest at point A and accelerates toward point B. Upon reaching B, it continues to accelerate toward C. If only motion along the line is allowed, what would a negative charge do if it were released from rest at point B? It would remain stationary. It would accelerate toward A. It would accelerate toward C.

It would accelerate toward A.

10.2 Kirchhoff's loop rule is a consequence of: The conservation of resistance The conservation of energy The conservation of charge The conservation of momentum

The conservation of energy (potential to be exact)

A car battery seems to be malfunctioning (not providing the proper voltage and current to start your car). While the car is off and you are not trying to start it, a friend uses a voltmeter to measure the voltage and finds that your battery voltage is 12.0 V, just as it is supposed to be. After the voltage check, you try to start your car again to no avail. Can you rule out the battery as the problem? Yes, the voltage was checked. No, there could still be something wrong with the battery.

No, there could still be something wrong with the battery.

7.1 A long, straight wire carries a current in a direction from left to right as shown in the figure. Point P is located above the wire in the plane of the screen. What is the direction of the magnetic field at point P? Into the screen Right Out of the screen Down Left Up

Out of the screen Apply Right-hand rule #2.

7.1 Suppose a small, positively charged particle moves past a positively charged sphere with speed V. Which one of the following vectors is parallel to the electric field lines of the sphere (at the location of the particle) the instant the particle passes the sphere? The acceleration of the particle. The velocity of the particle. None of these. The displacement of the particle.

The acceleration of the particle.

1.1 A positive charge is placed between the plates of a parallel plate capacitor and released from rest at Point B, as shown in the figure. In what direction does the charge move? The charge moves toward Point B. The charge remains at rest. The charge moves toward Point C.

The charge moves toward Point C.

10.1 Kirchhoff's junction rule is a consequence of: The conservation of resistance The conservation of energy The conservation of charge The conservation of momentum

The conservation of charge

In the previous question, the work done by the electrostatic force in moving the positive charge from Point B to Point C () would be equal to which of the following? The electrostatic potential energy at Point B (EPEB). The electrostatic potential energy at Point C (EPEC). The difference in the electrostatic potential energy between Points B and C (EPEB - EPEC). The sum of the electrostatic potential energy between Points B and C (EPEB + EPEC).

The difference in the electrostatic potential energy between Points B and C (EPEB - EPEC).

A charge of +2Q and -Q2 are located at two of the vertices of an equilateral triangle. Which of the following is true? The potential at the triangle's empty vertex is positive. The potential at the triangle's empty vertex is negative. The potential at the triangle's empty vertex is zero.

The potential at the triangle's empty vertex is zero. b) Consider the length of a side as 'a'Potential at the empty vertex = k(+2Q)/a + k(-2Q)/a= 2kQ/a - 2kQ/a= 0i.e, the potential at the empty vertex is zero.

3.1 A positive charge is moving with velocity v through a region of space where a uniform magnetic field exists everywhere into the screen, as the figure shows. What is the direction of the magnetic force on the charge just as it enters the field?

The right hand rule states that, to find the direction of the magnetic force on a positive moving charge, the thumb of the right hand point in the direction of v, the fingers in the direction of B, and the force (F) is directed perpendicular to the right hand palm.

4 A positively charged ebonite rod is brought close to a small ball. The rod does not touch the ball, which is made from a conducting material. The ball is electrically neutral. Which one of the following statements is true? The rod neither attracts nor repels the ball. The rod repels the ball. The rod attracts the ball. As the rod is brought closer to the ball, the force changes from an attractive force to a repulsive force.

The rod attracts the ball. The ball is electrically neutral (net charge equals zero). However, it is made from a conducting material, so it contains electrons that are free to move. The rod attracts some of these (negative) electrons to the side of the ball nearest the rod, leaving the opposite side of the ball positively charged. Since the negative side of the ball is closer to the positive rod than the positive side, a net attractive force arises.

Suppose a thin conducting wire connects two conducting spheres. A negatively charged rod is brought near one of the spheres, the wire between them is cut, and the charged rod is taken away. Which one of the following is true? The spheres will attract each other. There will be no electrostatic force between the spheres. The spheres will repel each other.

The spheres will attract each other.

6.2 What component of a DC electric motor ensures that the current is always in the proper direction to yield a torque that produces a continuous rotation of the coil? The brushes The shaft The split-ring commutator

The split-ring commutator

A capacitor is charged with a battery to a voltage and then disconnected from the battery. A dielectric is inserted between the plates. When the dielectric is inserted, what happens to the electrostatic potential energy stored in the capacitor? The stored energy increases. The stored energy decreases. The stored energy remains constant.

The stored energy decreases.

12.1 You have two identical capacitors of capacitance C. Which of the following configurations gives you the smallest equivalent capacitance? The two capacitors wired in parallel. One capacitor alone. The two capacitors wired in series.

The two capacitors wired in series.

Each of three objects carries a charge. As the drawing shows, objects A and B attract each other, and objects C and A also attract each other. Which one of the following statements concerning objects B and C is true? They attract each other. They repel each other. They neither attract nor repel each other. This question cannot be answered without additional information.

They repel each other. Suppose that A is positive and B is negative. Since C and A also attract each other, C must be negative. Thus, B and C repel each other, because they have like charges (both negative). Suppose, however, that A is negative and B is positive. Since C and A also attract each other, C must be positive. Again we conclude that B and C repeal each other, because they have like charges (both positive).

4.2 The figure shows a mass spectrometer that is calibrated to detect a particular charged particle whose mass is (path 1)? If the charged particles traveling along path 2 are an isotope of those traveling along path 1, how does the mass of particle 2 compare to the mass of particle 1? m1<m2 m1>m2

m1<m2 As we know that the magnetic field exerts the force which supplies the centripetal force here Hence mv2/r = qvB Therefore r = mv / qB So radiues is larger if mass is greater hence M1 is smaller than m2.