CH 20 & 21 Quizzes

How does the resistance of a copper wire change when both the length and diameter of the wire are doubled? (a)It decreases by a factor of two. (b)It increases by a factor of two. (c)It increases by a factor of four. (d)It decreases by a factor of four. (e)It does not change.

(a)It decreases by a factor of two.

Two materials have different resistivities. Two wires of the same length are made, one from each of the materials. Is it possible for each wire to have the same resistance? (a)Yes, if the material with the greater resistivity is used for a thinner wire. (b)Yes, if the material with the greater resistivity is used for a thicker wire. (c)It is not possible.

(b)Yes, if the material with the greater resistivity is used for a thicker wire.

What would happen to the current in a circuit if a voltmeter, inadvertently mistaken for an ammeter, were inserted into the circuit? The current would (a)increase markedly (b)decrease markedly (c)remain the same.

(b)decrease markedly

A toaster is designed to operate with a voltage of 120 , and a clothes dryer is designed to operate with a voltage of 240 . Based solely on this information, which appliance uses more power? (a)The toaster (b)The dryer (c)Insufficient information is given for an answer.

(c)Insufficient information is given for an answer. (A value for the current is also needed.)

An ideal ammeter has ________ resistance, whereas an ideal voltmeter has ________ resistance. (a)zero, zero (b)infinite, infinite (c)zero, infinite (d)infinite, zero

(c)zero, infinite

An ac circuit contains only a generator and a resistor. Which one of the following changes leads to the greatest average power being delivered to the circuit? (a)Double the peak voltage of the generator and double the resistance. (b)Double the resistance. (c)Double the peak voltage of the generator. (d)Double the peak voltage of the generator and reduce the resistance by a factor of two.

(d)Double the peak voltage of the generator and reduce the resistance by a factor of two.

Two circuits present the same resistance to the current. In one circuit the battery causing the flow of current has a voltage of 9.0 V , and the current is 3.0 A . In the other circuit the battery has a voltage of 1.5 V. What is the current in this other circuit?

0.50 A

Three capacitors are connected in parallel to a battery. How is the equivalent capacitance for this circuit determined? The equivalent capacitance is the sum of the three capacitances. Unlike resistors, an equivalent capacitance cannot be found by any simple means. The potential drop across each capacitor is measured and multiplied by each capacitance before adding them together. The equivalent capacitance is the sum of the three capacitances divided by three. In other words, the equivalent capacitance is the average capacitance in the circuit. A resistor is used to replace one capacitor at a time. Then, the current through the resistor is measured and used to determine the charge on each capacitor. The sum of the charges is then divided by the emf of the battery to find the equivalent capacitance.

The equivalent capacitance is the sum of the three capacitances.

A long, straight, vertical segment of wire traverses a magnetic field of magnitude 2.0 T in the direction shown in the diagram. The length of the wire that lies in the magnetic field is 0.060 m. When the switch is closed, a current of 4.0 A flows through the wire from point P to point Q. The wire will be pushed to the left. The wire will be pushed upward, out of the plane of the paper. The wire will be pushed to the right. The wire will have no net force acting on it. The wire will be pushed downward, into the plane of the paper

the wire will be pushed downward into the plane of the paper

The drawing shows a circuit that includes a bimetallic strip (made from brass and steel; see Section 12.4) with a resistance heater wire wrapped around it. When the switch is initially closed, a current appears in the circuit because charges flow through the heater wire (which becomes hot), the strip itself, the contact point, and the light bulb. The bulb glows in response. As long as the switch remains closed, does the bulb (a)continue to glow, (b)eventually turn off permanently, or (c)flash on and off?

(c)flash on and off?

Two identical light bulbs are connected to identical batteries in two different ways. In method A the bulbs are connected in parallel, and the parallel combination is connected between the one battery's terminals. In method B the bulbs are connected in series, and the series combination is connected between the other battery's terminals. What is the ratio of the power supplied by the battery in method A to the power supplied in method B? (a) 1/4 (b)4 (c) 1/2 (d)2 (e)1

4

Which one of the following statements is not a characteristic of a voltmeter? The voltmeter is not placed directly into a circuit. An ideal voltmeter has almost no resistance. The voltmeter measures the voltage between two points in a circuit. The voltmeter is designed to draw very little current from the circuit being measured. The voltmeter is designed to measure nearly the same voltage that is present when the meter is not connected.

An ideal voltmeter has almost no resistance

In analyzing circuits in which resistors are wired partially in series and partially in parallel, which one of the following statements describes the preferred approach to take to determine the equivalent resistance in the circuit? Find the sum of all the resistors. This is the equivalent resistance for the circuit. Add together all of the resistors in series, ignoring any wired in parallel as they do not significantly add to the equivalent resistance of the circuit. The sum of the resistors in series is the equivalent resistance. Add together all of the resistors in parallel, ignoring any wired in series as they do not significantly add to the equivalent resistance of the circuit. The sum of the resistors in parallel is the equivalent resistance. Break the circuit into smaller parts and find an equivalent resistance for each part. Then continue this process until all of the parts are added together correctly either in series or parallel until a single equivalent resistance is found.

Break the circuit into smaller parts and find an equivalent resistance for each part. Then continue this process until all of the parts are added together correctly either in series or parallel until a single equivalent resistance is found.

Three capacitors are connected in series to a battery. Which one of the following statements concerning this situation is true? An equivalent capacitance can be found for capacitors connected in series, but not when they are connected in parallel. The battery must move more charge when the capacitors are connected in series than when connected in parallel. The equivalent capacitance is less than the sum of the individual capacitances. The amount of charge on each capacitor depends on its capacitance. If the capacitors have different capacitances, they will have differing amounts of charge on their plates. The equivalent capacitance is equal to the sum of the individual capacitances.

The equivalent capacitance is less than the sum of the individual capacitances.

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? he top loop moves to the right; the bottom loop moves to the right. The loops remain in the positions shown. The loops attract each other. Both loops move to the left. The loops repel each other.

The loops attract eachother

Which one of the following statements concerning the magnetic force on a charged particle in a magnetic field is true? Entry field with correct answer The magnetic force is zero if the particle moves perpendicular to the field. The magnetic force is a maximum if the particle moves parallel to the field. The magnetic force acts in the direction of motion for a positively charged particle. The magnetic force is a maximum if the particle is stationary. The magnetic force depends on the component of the particle's velocity that is perpendicular to the field.

The magnetic force depends on the component of the particle's velocity that is perpendicular to the field.

Which one of the following statements best explains why a constant magnetic field can do no work on a moving charged particle? Entry field with correct answer The magnetic field is conservative. The magnetic field is a vector and work is a scalar quantity. The magnetic force is a velocity dependent force. The magnetic force is always perpendicular to the velocity of the particle. The electric field associated with the particle cancels the effect of the magnetic field on the particle.

The magnetic force is always perpendicular to the velocity of the particle.

Which of the following statements concerning resistors that are wired in parallel is true? The current through each resistor is necessarily the same. The equivalent resistance for the resistors in the circuit is the product of the individual resistances. The equivalent resistance for the resistors in the circuit is the sum of the individual resistances. The voltage across each resistor is necessarily the same. The equivalent resistance for the resistors in the circuit is the average of the individual resistances.

The voltage across each resistor is necessarily the same.

You have four resistors, each of which has a resistance . It is possible to connect these four together so that the equivalent resistance of the combination is also . How many ways can you do it? There is more than one way.

There are two ways. One is to form two groups of two parallel resistors and then connect the groups in series. The other is to form two groups of two series resistors and then connect the groups in parallel.

Which one of the following statements concerning permanent magnets is false? The direction of a magnetic field is indicated by the north pole of a compass. The north pole of a permanent magnet is attracted to a south pole. 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. All permanent magnets are surrounded by a magnetic field.

When a permanent magnet is cut in half, one piece will be a north pole and one piece will be a south pole.

Two resistors can be either connected to a battery in series or in parallel. In which case, if either, is the equivalent resistance the smallest? When the two resistors are wired in parallel, the equivalent resistance is less than if they are wired in series. When the two resistors are wired in series, the equivalent resistance is less than if they are wired in parallel. Both series and parallel wiring will result in the same equivalent resistance. It is not possible to know which method of wiring will result in the lowest equivalent resistance without knowing the values of the two resistances.

When the two resistors are wired in parallel, the equivalent resistance is less than if they are wired in series.

Complete the following statement: The magnetic field around a current-carrying, circular loop is most like that of Entry field with correct answer the earth. a short bar magnet. a current-carrying, rectangular loop. two long straight wires that carry currents in opposite directions. a long straight wire that carries a current.

a short bar magnet

Two particles move through a uniform magnetic field that is directed out of the plane of the page. The figure shows the paths taken by the two particles as they move through the field. The particles are not subject to any other forces or fields. Which one of the following statements concerning these particles is true?

charge 1 and 2 are negative

The fact that the sum of the currents entering any junction in an electric circuit must be equal to the sum of the currents leaving the junction is an expression of what principle? conservation of momentum Archimedes' Principle Heisenberg uncertainty principle conservation of charge conservation of energy

conservation of charge

A current-carrying, rectangular coil of wire is placed in a magnetic field. The magnitude of the torque on the coil is not dependent upon which one of the following quantities? the direction of the current in the loop the orientation of the loop the length of the sides of the loop the area of the loop the magnitude of the current in the loop

direction of the current in the lops

An electron traveling horizontally enters a region where a uniform magnetic field is directed into the plane of the paper as shown. Which one of the following phrases most accurately describes the motion of the electron once it has entered the field? downward and parabolic upward, along a straight line upward and parabolic upward and circular downward and circular

downward and circular

Complete the following statement: The sum of the magnitudes of the currents directed into a junction equals the sum of the magnitudes of the currents directed out of the junction. is greater than the total current directed out of the junction. equals the current that is directed along one of the lines out of the junction. is divided equally among the number of lines directed out of the junction. is less than the total current directed out of the junction.

equals the sum of the magnitudes of the currents directed out of the junction

Complete the following statement: Around any closed-circuit loop, the sum of the potential drops must increase with the addition of any resistor. equals the sum of the potential rises. equals the emf of the battery. is the same potential drop as in any other loop. must equal zero (like the sum of the potential rises).

equals the sum of the potential rises

In circuit A the battery that supplies energy has twice as much voltage as the battery in circuit B. However, the current in circuit A is only one-half the current in circuit B. Circuit A presents ________ the resistance to the current that circuit B does. (a)twice (b)one-half (c)the same (d)four times (e)one-fourth

four times

A car has two headlights, and their power is derived from the car's battery. The filament in one burns out, but the other headlight stays on. Are the headlights connected in series or in parallel?

in parallel

Which one of the following terms describes the resistance that a battery or a generator has in a circuit? super resistance internal resistance electroresistance critical resistance terminal resistance

internal resistance

When an incandescent light bulb is turned on, a constant voltage is applied across the tungsten filament, which then becomes white hot. The temperature coefficient of resistivity for tungsten is a positive number. What happens to the power delivered to the bulb as the filament heats up? (a)It decreases. (b)It increases. (c)It remains constant.

it decreases

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. What is the direction of the magnetic field at point P due to the current in the wire? to the left of the page to the right of page toward the bottom of the page into the plane of the page out of the plane of the page

out of the plane of the page