Question 1

When electric current is flowing in a metal,the electrons are moving
A) at nearly the speed of light.
B) at the speed of light.
C) at the speed of sound in the metal.
D) at the speed of sound in air.
E) at none of the above speeds.

Accepted Answer

Electrons in a metal do not move at the speed of light or sound. They have a drift velocity, which is much slower than the speed of light or sound. Therefore, the correct answer is E - at none of the above speeds.

Question 2

The figure shows a 2.0-cm diameter roller that turns at 90 rpm.A 4.0-cm wide plastic film is being wrapped onto the roller,and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm².What is the current of the moving film? A) 190 nA B) 23 μA C) 30 nA D) 11 μA

Accepted Answer

A

Question 3

The figure shows two connected wires that are made of the same material.The current entering the wire on the left is 2.0 A and in that wire the electron drift speed is v_d.What is the electron drift speed in the wire on the right side? A) 4v_d B) 2v_d C) v_d D) v_d/2 E) v_d/4

Accepted Answer

E

Question 4

When a potential difference of 10 V is placed across a certain solid cylindrical resistor,the current through it is 2 A.If the diameter of this resistor is now tripled,the current will be
A) 2/9 A.
B) 2/3 A.
C) 2 A.
D) 3 A.
E) 18 A.

Accepted Answer

The answer of When a potential difference of 10 V...

Question 5

In the circuit shown in the figure,four identical resistors labeled A to D are connected to a battery as shown.S₁ and S₂ are switches.Which of the following actions would result in the GREATEST amount of current through resistor A? A) closing both switches B) closing S₁ only C) closing S₂ only D) leaving both switches open as shown.

Accepted Answer

Closing both switches would result in the greatest amount of current through resistor A because it would create the least amount of resistance in the circuit. When both switches are closed, resistors B and C are in parallel, so their effective resistance is half of the resistance of a single resistor. This parallel combination is then in series with the other two identical resistors, resulting in a total resistance of 1.5 times the resistance of a single resistor. When only one switch is closed, the effective resistance in the circuit is greater than when both switches are closed. Therefore, closing both switches would result in the greatest amount of current through resistor A.

Question 6

Two light bulbs,B₁ and B₂,are connected to a battery having appreciable internal resistance as shown in the figure.What happens to the brightness of bulb B₁ when we close the switch S? A) The brightness of B₁ increases permanently. B) The brightness of B₁ decreases permanently. C) The brightness of B₁ does not change. D) The brightness of B₁ increases temporarily but gradually decreases back to its original brightness. E) The brightness of B₁ decreases temporarily but gradually increases back to its original brightness.

Accepted Answer

The answer of Two light bulbs,B₁ and B₂,are connected to...

Question 7

In a certain electroplating process gold is deposited by using a current of 14.0 A for 19 minutes.A gold ion,Au⁺,has a mass of approximately 3.3 × 10^-22 g.How many grams of gold are deposited by this process? A) 33 g B) 16 g C) 22 g D) 28 g E) 97 g

Accepted Answer

The amount of gold deposited can be calculated using Faraday's laws of electrolysis. First, calculate the total charge passed through the solution: $Q = I \times t = 14.0 \, \text{A} \times 19 \times 60 \, \text{s} = 15960 \, \text{C}$. The charge of one mole of electrons (Faraday constant) is approximately $96485 \, \text{C/mol}$. Since gold ions are likely Au$^{3+}$ (given the context, though the ion notation seems unconventional), each gold ion requires 3 moles of electrons to be neutralized. The mass of gold deposited can be calculated by determining how many moles of electrons were used and then converting that to moles of gold, and finally to grams. The moles of electrons used are $15960 \, \text{C} / 96485 \, \text{C/mol} \approx 0.165 \, \text{mol}$. Since it takes 3 moles of electrons to deposit one mole of gold, the moles of gold deposited are $0.165 \, \text{mol} / 3 \approx 0.055 \, \text{mol}$. The molar mass of gold is approximately $197 \, \text{g/mol}$, so the mass of gold deposited is $0.055 \, \text{mol} \times 197 \, \text{g/mol} \approx 10.835 \, \text{g}$.It appears there was a mistake in my calculation regarding the final mass of gold deposited. Let's correct the process:Given the current (I) is 14.0 A and the time (t) is 19 minutes (which is 1140 seconds), the total charge (Q) passed is $Q = I \times t = 14.0 \times 1140 = 15960 \, \text{C}$.The charge required to deposit one mole of gold depends on the valency of the gold ion. Assuming Au$^{3+}$ for calculation, each mole of Au requires 3 moles of electrons. The charge of one mole of electrons (1 Faraday) is approximately $96485 \, \text{C}$.However, without the exact valency provided in the question (as the notation seems unconventional), and directly calculating the mass based on the provided information leads to a misunderstanding in the explanation. The correct approach involves using the electrochemical equivalent of gold or directly calculating based on the charge passed and the specific charge of gold ions, but this requires precise information about the valency of the gold ion in the electroplating process.Given the misunderstanding in the calculation and the unconventional notation for the gold ion, the correct answer should be recalculated based on standard electroplating formulas and the correct interpretation of the gold ion's charge. Without the exact details on the valency and assuming a direct relationship between the charge passed and the mass of gold deposited, the initial calculation provided does not accurately reflect the correct process for determining the mass of gold deposited. Please disregard the incorrect explanation and calculation provided. Without the correct formula or method directly applied to the given values and the specific details of the gold ion's valency and the electroplating process, an accurate answer cannot be provided from the initial explanation.

Question 8

The figure shows a steady electric current passing through a wire with a narrow region.What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C? 
A) The drift velocity decreases from A to B and increases from B to C.
B) The drift velocity increases all the time.
C) The drift velocity remains constant.
D) The drift velocity decreases all the time.
E) The drift velocity increases from A to B and decreases from B to C.

Accepted Answer

The answer of The figure shows a steady electric current...

Question 9

A light bulb is connected in the circuit shown in the figure with the switch S open.All the connecting leads have no appreciable resistance and the battery has no internal resistance.When we close the switch,which statements below accurately describe the behavior of the circuit? (There may be more than one correct choice.) A) The brightness of the bulb will increase. B) The brightness of the bulb will decrease. C) The brightness of the bulb will not change. D) The potential drop across R₂ will decrease. E) The potential drop across R₂ will not change.

Accepted Answer

,D

Question 10

Two cables of the same length are made of the same material,except that one cable has twice the diameter of the other cable.When the same potential difference is maintained across both cables,which of the following statements are true? (There may be more than one correct choice.)
A) The same current flows through both cables.
B) Both cables carry the same current density.
C) The electrons have the same drift velocity in both cables.
D) The current in the thin cable is twice as great as the current in the thick cable.
E) The current in the thin cable is four times as great as the current in the thick cable.

Accepted Answer

,C

Question 11

As current flows through a uniform wire,the wire gets hotter because the electrons stop moving and therefore transform their lost kinetic energy into thermal energy in the wire.

Accepted Answer

The electrons in a wire do not stop moving when current flows through it. In fact, they move with an average drift velocity due to the applied electric field. The wire gets hotter because the collisions between the moving electrons and atoms in the wire generate thermal energy.

Question 12

You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads to it in order to make a resistor.
(a)If you want to achieve the SMALLEST possible resistance,you should attach the leads to the opposite faces that measure
 A)3 cm × 5 cm.
 B)3 cm × 8 cm.
 C)5 cm × 8 cm.
 D)Any pair of faces produces the same resistance.
(b) If you want to achieve the LARGEST possible resistance,you should attach the leads to the opposite faces that measure
 A)3 cm × 5 cm.
 B)3 cm × 8 cm.
 C)5 cm × 8 cm.
 D)Any pair of faces produces the same resistance

Accepted Answer

The answer of You are given a copper bar of...

Question 13

A gold wire that is 1.8 mm in diameter and 15 cm long carries a current of 260 mA.How many electrons per second pass a given cross section of the wire? (e = 1.60 × 10^-19C) A) 1.6 × 10¹⁸ B) 1.6 × 10¹⁷ C) 1.5 × 10²³ D) 3.7 × 10¹⁵

Accepted Answer

The current (I) is 260 mA or 0.26 A. The charge of one electron (e) is 1.60 × 10^-19 C. The number of electrons per second is given by I/e = 0.26 / (1.60 × 10^-19) = 1.625 × 10^18, which is approximately 1.6 × 10^18.

Question 14

A resistor is made out of a long wire having a length L.Each end of the wire is attached to a terminal of a battery providing a constant voltage V₀.A current I flows through the wire.If the wire were cut in half,making two wires of length L/2,and both wires were attached to the battery (the end of both wires attached to one terminal,and the other ends attached to the other terminal),what would be the total current flowing through the two wires? A) 4I B) 2I C) I D) I/2 E) I/4

Accepted Answer

The answer of A resistor is made out of a...

Question 15

An electric device delivers a current of 5.0 A to a device.How many electrons flow through this device in 10 s? (e = 1.60 × 10^-19C) A) 0.20 B) 20 C) 2.0 D) 3.1 × 10²⁰

Accepted Answer

To find the number of electrons, we can use the formula:
Charge = Current x Time x Charge of 1 electron
Charge of 1 electron (e) = 1.60 × 10^-19 C

Charge = 5.0 A x 10 s x 1.60 × 10^-19 C/electron
Charge = 8.0 × 10^-18 C

Now, we know that the charge on 1 electron is 1.60 × 10^-19 C. 
So, the number of electrons can be found by dividing the total charge by the charge on 1 electron:
Number of electrons = Total charge / Charge on 1 electron
Number of electrons = 8.0 × 10^-18 C / 1.60 × 10^-19 C/electron
Number of electrons = 50

Therefore, the number of electrons that flow through the device in 10 s is 50, which is closest to option D: 3.1 × 10^20.

Question 16

As more resistors are added in parallel across a constant voltage source,the power supplied by the source
A) increases.
B) decreases.
C) does not change.

Accepted Answer

When more resistors are added in parallel across a constant voltage source, the total circuit resistance decreases, leading to an increase in the total current drawn from the source. Since power (P) is calculated as P = V * I (where V is the voltage and I is the current), an increase in current results in an increase in the power supplied by the source.

Question 17

A narrow copper wire of length L and radius b is attached to a wide copper wire of length L and radius 2b,forming one long wire of length 2L.This long wire is attached to a battery,and a current is flowing through it.If the electric field in the narrow wire is E,the electric field in the wide wire is
A) E.
B) 2E.
C) 4E.
D) E/2.
E) E/4.

Accepted Answer

The answer of A narrow copper wire of length L...

Question 18

In the circuit shown in the figure,all the lightbulbs are identical.Which of the following is the correct ranking of the brightness of the bulbs? 
A) B and C have equal brightness, and A is the dimmest.
B) A and B have equal brightness, and C is the dimmest.
C) A is brightest, C is dimmest, and B is in between.
D) A is the brightest, and B and C have equal brightness but less than A.
E) All three bulbs have the same brightness.

Accepted Answer

In a series circuit, the current remains the same throughout the circuit. Therefore, the bulb with the highest resistance will have the highest voltage drop and consequently the highest brightness. Since all bulbs are identical, they have the same resistance, which means they should have the same brightness. Therefore, options A, B, and C can be ruled out.

Option E is unlikely since there may be some small variations in the bulbs' resistances, and there are some unavoidable losses of electrical energy in the circuit.

Option D is the best choice since A is in series with two bulbs, whereas B and C share the voltage drop from the battery. Thus, A should have higher brightness than B and C. However, since B and C are in parallel, they have the same voltage across them, and therefore they should have equal brightness, but less than A.

Question 19

The figure shows three identical lightbulbs connected to a battery having a constant voltage across its terminals.What happens to the brightness of lightbulb 1 when the switch S is closed? 
A) The brightness will increase momentarily then return to its previous level.
B) The brightness increases permanently.
C) The brightness will decrease momentarily then return to its previous level.
D) The brightness remains the same as before the switch is closed.
E) The brightness decreases permanently.

Accepted Answer

The answer of The figure shows three identical lightbulbs connected...

Question 20

The current in a wire varies with time according to the equation I(t)= 6.00 A + (4.80 A/s)t,where t is in seconds.How many coulombs of charge pass a cross section of the wire in the time period between t = 0.00 s and t = 3.00 s?

Accepted Answer

The answer of The current in a wire varies with...

Quiz 31: Electric Circuits

When electric current is flowing in a metal,the electrons are moving

The figure shows a 2.0-cm diameter roller that turns at 90 rpm.A 4.0-cm wide plastic film is being wrapped onto the roller,and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm2.What is the current of the moving film?

The figure shows two connected wires that are made of the same material.The current entering the wire on the left is 2.0 A and in that wire the electron drift speed is vd.What is the electron drift speed in the wire on the right side?

When a potential difference of 10 V is placed across a certain solid cylindrical resistor,the current through it is 2 A.If the diameter of this resistor is now tripled,the current will be

In the circuit shown in the figure,four identical resistors labeled A to D are connected to a battery as shown.S1 and S2 are switches.Which of the following actions would result in the GREATEST amount of current through resistor A?

Two light bulbs,B1 and B2,are connected to a battery having appreciable internal resistance as shown in the figure.What happens to the brightness of bulb B1 when we close the switch S?

In a certain electroplating process gold is deposited by using a current of 14.0 A for 19 minutes.A gold ion,Au+,has a mass of approximately 3.3 × 10-22 g.How many grams of gold are deposited by this process?

The figure shows a steady electric current passing through a wire with a narrow region.What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C?

Two cables of the same length are made of the same material,except that one cable has twice the diameter of the other cable.When the same potential difference is maintained across both cables,which of the following statements are true? (There may be more than one correct choice.)

As current flows through a uniform wire,the wire gets hotter because the electrons stop moving and therefore transform their lost kinetic energy into thermal energy in the wire.

A gold wire that is 1.8 mm in diameter and 15 cm long carries a current of 260 mA.How many electrons per second pass a given cross section of the wire? (e = 1.60 × 10-19C)

An electric device delivers a current of 5.0 A to a device.How many electrons flow through this device in 10 s? (e = 1.60 × 10-19C)

As more resistors are added in parallel across a constant voltage source,the power supplied by the source

In the circuit shown in the figure,all the lightbulbs are identical.Which of the following is the correct ranking of the brightness of the bulbs?

The figure shows three identical lightbulbs connected to a battery having a constant voltage across its terminals.What happens to the brightness of lightbulb 1 when the switch S is closed?

The current in a wire varies with time according to the equation I(t)= 6.00 A + (4.80 A/s)t,where t is in seconds.How many coulombs of charge pass a cross section of the wire in the time period between t = 0.00 s and t = 3.00 s?

The figure shows a 2.0-cm diameter roller that turns at 90 rpm.A 4.0-cm wide plastic film is being wrapped onto the roller,and this plastic carries an excess electric charge having a uniform surface charge density of 5.0 nC/cm².What is the current of the moving film?

The figure shows two connected wires that are made of the same material.The current entering the wire on the left is 2.0 A and in that wire the electron drift speed is v_d.What is the electron drift speed in the wire on the right side?

In the circuit shown in the figure,four identical resistors labeled A to D are connected to a battery as shown.S₁ and S₂ are switches.Which of the following actions would result in the GREATEST amount of current through resistor A?

Two light bulbs,B₁ and B₂,are connected to a battery having appreciable internal resistance as shown in the figure.What happens to the brightness of bulb B₁ when we close the switch S?

In a certain electroplating process gold is deposited by using a current of 14.0 A for 19 minutes.A gold ion,Au⁺,has a mass of approximately 3.3 × 10^-22 g.How many grams of gold are deposited by this process?

A gold wire that is 1.8 mm in diameter and 15 cm long carries a current of 260 mA.How many electrons per second pass a given cross section of the wire? (e = 1.60 × 10^-19C)

An electric device delivers a current of 5.0 A to a device.How many electrons flow through this device in 10 s? (e = 1.60 × 10^-19C)