Question 1

The conservation of energy in an electric circuit is closely related to which of the following?

Accepted Answer

A) Ohm's law 
B) Kirchhoff's junction rule 
C) Kirchhoff's loop rule 
D) Newton's laws 
E) Ampère's law 
A) Ohm's law 
B) Kirchhoff's junction rule 
C) Kirchhoff's loop rule 
D) Newton's laws 
E) Ampère's law

Question 2

Since you cannot afford expensive cable to hook up between your loudspeaker and music amplifier,you try some common 14-gauge (diameter = 1.628 mm)copper wire.If the total length of the wire (there and back)used for each speaker to amplifier hookup was 10 m,then calculate the resistance in the wire for one channel.($\rho$(Cu)= 1.7 $\times$ 10-8 $\Omega$/m)

Accepted Answer

A) 2.6 $\times$ 10-2 $\Omega$ 
B) 2.0 $\times$ 10-2 $\Omega$ 
C) 4.1 $\times$ 10-3 $\Omega$ 
D) 8.2 $\times$ 10-2 $\Omega$ 
E) 1.6 $\times$ 10-1 $\Omega$ 
A) 2.6 $\times$ 10-2 $\Omega$ 
B) 2.0 $\times$ 10-2 $\Omega$ 
C) 4.1 $\times$ 10-3 $\Omega$ 
D) 8.2 $\times$ 10-2 $\Omega$ 
E) 1.6 $\times$ 10-1 $\Omega$

Question 3

In a certain particle accelerator,a current of 300 $\mu$A is carried by a 4.00-MeV proton beam that has a radius of 1.30 mm.The mass of a proton is 1.67 $\times$ 10-27 kg.If the beam hits a target,how many protons hit the target in 3 s?

Accepted Answer

A) 1.55 $\times$ 1015  
B) 8.64 $\times$ 1015  
C) 3.42 $\times$ 1015  
D) 4.29 $\times$ 1015  
E) None of these is correct. 
A) 1.55 $\times$ 1015  
B) 8.64 $\times$ 1015  
C) 3.42 $\times$ 1015  
D) 4.29 $\times$ 1015  
E) None of these is correct.

Question 4

Which of the following statements is false?

Accepted Answer

A) An electric field is needed to produce an electric current. 
B) A potential difference between two points is needed to produce an electric current. 
C) For a steady current to flow in a wire,the wire must be part of a closed circuit. 
D) The electric field is constant along all parts of the circuit when a steady current is flowing. 
E) The electric current in a wire is proportional to the drift velocity of the charges. 
A) An electric field is needed to produce an electric current. 
B) A potential difference between two points is needed to produce an electric current. 
C) For a steady current to flow in a wire,the wire must be part of a closed circuit. 
D) The electric field is constant along all parts of the circuit when a steady current is flowing. 
E) The electric current in a wire is proportional to the drift velocity of the charges.

Question 5

Battery A has a relatively high internal resistance,whereas battery B has a low internal resistance.If both batteries provide the same current to some external circuitry,which of the following statements is likely to be true?

Accepted Answer

A) Battery A is warmer to the touch than battery B. 
B) Battery B is warmer to the touch than battery A. 
C) Battery A is cooler to the touch than battery B. 
D) Both batteries are equally warm to the touch. 
E) The emf of both batteries must be known to predict their warmth to the touch. 
A) Battery A is warmer to the touch than battery B. 
B) Battery B is warmer to the touch than battery A. 
C) Battery A is cooler to the touch than battery B. 
D) Both batteries are equally warm to the touch. 
E) The emf of both batteries must be known to predict their warmth to the touch.

Question 6

The power dissipated in each of two resistors is the same.The potential drop across resistor A is twice that across resistor B.If the resistance of resistor B is R,what is the resistance of A?

Accepted Answer

A) R 
B) 2R 
C) R/2 
D) 4R 
E) R/4 
A) R 
B) 2R 
C) R/2 
D) 4R 
E) R/4

Question 7

A motor running from a 220-V line is lifting a mass of 35 kg against Earth's gravity at a constant speed of 6.0 m/s.If we assume 100% efficiency,the current required is

Accepted Answer

A) 0.27 A 
B) 9.4 A 
C) 7.7 A 
D) 3.3 A 
E) 4.7 A 
A) 0.27 A 
B) 9.4 A 
C) 7.7 A 
D) 3.3 A 
E) 4.7 A

Question 8

Each of three identical electric heaters is rated at 1000 W when operated across 100-V lines.When the three are connected in series across a 120-V line,at what rate is electric energy converted to heat energy? (Neglect variation of resistance with temperature.)

Accepted Answer

A) 0.48 kW 
B) 1.0 kW 
C) 1.2 kW 
D) 3.0 kW 
E) 3.6 kW 
A) 0.48 kW 
B) 1.0 kW 
C) 1.2 kW 
D) 3.0 kW 
E) 3.6 kW

Question 9

If electric energy costs 10 cents per kilowatt-hour,how many cents does it cost to keep a 660-W toaster in steady operation for 30 min?

Accepted Answer

A) 15 cents 
B) 12 cents 
C) 6.9 cents 
D) 3.3 cents 
E) 1.7 cents 
A) 15 cents 
B) 12 cents 
C) 6.9 cents 
D) 3.3 cents 
E) 1.7 cents

Question 10

A battery is connected to a series combination of a switch,a resistor,and an initially uncharged capacitor.The switch is closed at t = 0.Which of the following statements is true?

Accepted Answer

A) As the charge on the capacitor increases,the current increases. 
B) As the charge on the capacitor increases,the voltage drop across the resistor increases. 
C) As the charge on the capacitor increases,the current remains constant. 
D) As the charge on the capacitor increases,the voltage drop across the capacitor decreases. 
E) As the charge on the capacitor increases,the voltage drop across the resistor decreases. 
A) As the charge on the capacitor increases,the current increases. 
B) As the charge on the capacitor increases,the voltage drop across the resistor increases. 
C) As the charge on the capacitor increases,the current remains constant. 
D) As the charge on the capacitor increases,the voltage drop across the capacitor decreases. 
E) As the charge on the capacitor increases,the voltage drop across the resistor decreases.

Question 11

The total charge flowing per hour past a given point in a piece of electrical equipment rated at 550 kW and 110 V is

Accepted Answer

A) 1.8 $\times$ 107 C 
B) 3.0 $\times$ 104 C 
C) 3.3 $\times$ 104 C 
D) 2.4 $\times$ 103 C 
E) impossible to determine without more information. 
A) 1.8 $\times$ 107 C 
B) 3.0 $\times$ 104 C 
C) 3.3 $\times$ 104 C 
D) 2.4 $\times$ 103 C 
E) impossible to determine without more information.

Question 12

A 12-V car battery may supply 60 A for 2.5 s in order for the starter motor to start the engine.Calculate how much electrical energy has been used.

Accepted Answer

A) 1.8 $\times$ 103 J 
B) 2.2 $\times$ 104 J 
C) 7.2 $\times$ 102 J 
D) 3.6 $\times$ 103 J 
E) 4.5 $\times$ 103 J 
A) 1.8 $\times$ 103 J 
B) 2.2 $\times$ 104 J 
C) 7.2 $\times$ 102 J 
D) 3.6 $\times$ 103 J 
E) 4.5 $\times$ 103 J

Question 13

If two elements of a circuit are in parallel,they must have the same

Accepted Answer

A) charge. 
B) potential difference across them. 
C) resistance. 
D) potential difference across them and the same charge. 
E) current. 
A) charge. 
B) potential difference across them. 
C) resistance. 
D) potential difference across them and the same charge. 
E) current.

Question 14

A 1.2-$\mu$F capacitor in a flash camera is charged by a 1.5-V battery.When the camera flashes,this capacitor is discharged through a resistor.The time constant of the circuit is 10 ms.What is the value of the resistance?

Accepted Answer

A) 8.0 $\times$ 10-2 $\Omega$ 
B) 0.12 $\Omega$ 
C) 12 k$\Omega$ 
D) 8.3 k$\Omega$ 
E) 3.1 k$\Omega$ 
A) 8.0 $\times$ 10-2 $\Omega$ 
B) 0.12 $\Omega$ 
C) 12 k$\Omega$ 
D) 8.3 k$\Omega$ 
E) 3.1 k$\Omega$

Question 15

Use the diagram for the next problem:  
-The switch S is initially at position b for a long time.It is then switched to position a.Describe what happens to the light bulb as a function of time when the switch is flipped from b to a?

Accepted Answer

A) The light bulb was on but goes off immediately. 
B) The light bulb was off and stays off. 
C) The light bulb was on but its brightness decreases with time and eventually goes off. 
D) The light bulb was on and stays on. 
E) The light bulb was off.It then lights up but the brightness decreases with time and eventually goes off. 
A) The light bulb was on but goes off immediately. 
B) The light bulb was off and stays off. 
C) The light bulb was on but its brightness decreases with time and eventually goes off. 
D) The light bulb was on and stays on. 
E) The light bulb was off.It then lights up but the brightness decreases with time and eventually goes off.

Question 16

In a parallel circuit,

Accepted Answer

A) the current is the same in every branch. 
B) the potential drop is the sum of those in all branches. 
C) the potential drop is the same for each element of the parallel circuit. 
D) the heat generated is the same in all branches. 
E) the resistance is the sum of the resistances of the branches. 
A) the current is the same in every branch. 
B) the potential drop is the sum of those in all branches. 
C) the potential drop is the same for each element of the parallel circuit. 
D) the heat generated is the same in all branches. 
E) the resistance is the sum of the resistances of the branches.

Question 17

A 10-gauge copper wire (diameter = 2.588 mm,$\rho$ = 1.7 $\times$ 10-8 $\Omega$ · m)has a total resistance of 0.32 $\Omega$.How long is the wire?

Accepted Answer

A) 4.0 $\times$ 102 m 
B) 1.6 km 
C) 99 m 
D) 31 m 
E) 65 m 
A) 4.0 $\times$ 102 m 
B) 1.6 km 
C) 99 m 
D) 31 m 
E) 65 m

Question 18

Two resistors are connected in series across a potential difference.If the current carried by resistor A is I,what is the current carried by B?

Accepted Answer

A) I 
B) 2I 
C) I/2 
D) 4I 
E) I/4 
A) I 
B) 2I 
C) I/2 
D) 4I 
E) I/4

Question 19

The conservation of charge in an electric circuit is closely related to which of the following?

Accepted Answer

A) Ohm's law 
B) Kirchhoff's junction rule 
C) Kirchhoff's loop rule 
D) Newton's laws 
E) Ampère's law 
A) Ohm's law 
B) Kirchhoff's junction rule 
C) Kirchhoff's loop rule 
D) Newton's laws 
E) Ampère's law

Question 20

The same potential difference is applied across two wires.Wire A carries twice the current of wire B.If the resistance of wire B is R,what is the resistance of wire A?

Accepted Answer

A) R 
B) 2R 
C) R/2 
D) 4R 
E) R/4 
A) R 
B) 2R 
C) R/2 
D) 4R 
E) R/4

Exam 25: Electric Current and Direct-Current Circuits

The conservation of energy in an electric circuit is closely related to which of the following?

In a certain particle accelerator,a current of 300 μ\muμ A is carried by a 4.00-MeV proton beam that has a radius of 1.30 mm.The mass of a proton is 1.67 ×\times× 10-27 kg.If the beam hits a target,how many protons hit the target in 3 s?

Which of the following statements is false?

Battery A has a relatively high internal resistance,whereas battery B has a low internal resistance.If both batteries provide the same current to some external circuitry,which of the following statements is likely to be true?

The power dissipated in each of two resistors is the same.The potential drop across resistor A is twice that across resistor B.If the resistance of resistor B is R,what is the resistance of A?

A motor running from a 220-V line is lifting a mass of 35 kg against Earth's gravity at a constant speed of 6.0 m/s.If we assume 100% efficiency,the current required is

Each of three identical electric heaters is rated at 1000 W when operated across 100-V lines.When the three are connected in series across a 120-V line,at what rate is electric energy converted to heat energy? (Neglect variation of resistance with temperature.)

If electric energy costs 10 cents per kilowatt-hour,how many cents does it cost to keep a 660-W toaster in steady operation for 30 min?

A battery is connected to a series combination of a switch,a resistor,and an initially uncharged capacitor.The switch is closed at t = 0.Which of the following statements is true?

The total charge flowing per hour past a given point in a piece of electrical equipment rated at 550 kW and 110 V is

A 12-V car battery may supply 60 A for 2.5 s in order for the starter motor to start the engine.Calculate how much electrical energy has been used.

If two elements of a circuit are in parallel,they must have the same

A 1.2- μ\muμ F capacitor in a flash camera is charged by a 1.5-V battery.When the camera flashes,this capacitor is discharged through a resistor.The time constant of the circuit is 10 ms.What is the value of the resistance?

Use the diagram for the next problem: -The switch S is initially at position b for a long time.It is then switched to position a.Describe what happens to the light bulb as a function of time when the switch is flipped from b to a?

In a parallel circuit,

A 10-gauge copper wire (diameter = 2.588 mm, ρ\rhoρ = 1.7 ×\times× 10-8 Ω\OmegaΩ · m)has a total resistance of 0.32 Ω\OmegaΩ .How long is the wire?

Two resistors are connected in series across a potential difference.If the current carried by resistor A is I,what is the current carried by B?

The conservation of charge in an electric circuit is closely related to which of the following?

The same potential difference is applied across two wires.Wire A carries twice the current of wire B.If the resistance of wire B is R,what is the resistance of wire A?

Systems of Measurement

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Motion in Two and Three Dimensions

Newtons Laws

Applications of Newtons Laws

Work and Energy

Conservation of Energy

Systems of Particles and Conservation of Linear Momentum

Rotation

Conservation of Angular Momentum

Gravity

Static Equilibrium and Elasticity

Fluids

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Wave Motion

Superposition and Standing Waves

Temperature and the Kinetic Theory of Gases

Heat and the First Law of Thermodynamics

The Second Law of Thermodynamics

Thermal Properties and Processes

The Electric Field I: Discrete Charge Distributions

The Electric Field Ii: Continuous Charge Distributions

Electric Potential

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Alternating-Current Circuits

Maxwells Equations and Electromagnetic Waves

Properties of Light

Optical Images

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Wave Particle Duality and Quantum Physics

Applications of the Schrodinger Equation

Atoms

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Solids and the Theory of Conduction

Relativity

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Elementary Particles and the Beginning of the Universe

Filters

In a certain particle accelerator,a current of 300 $\mu$ A is carried by a 4.00-MeV proton beam that has a radius of 1.30 mm.The mass of a proton is 1.67 $\times$ 10^-27 kg.If the beam hits a target,how many protons hit the target in 3 s?

A 1.2- $\mu$ F capacitor in a flash camera is charged by a 1.5-V battery.When the camera flashes,this capacitor is discharged through a resistor.The time constant of the circuit is 10 ms.What is the value of the resistance?

A 10-gauge copper wire (diameter = 2.588 mm, $\rho$ = 1.7 $\times$ 10^-8 $\Omega$ · m)has a total resistance of 0.32 $\Omega$ .How long is the wire?