PS III Exam 2.1

A 400-W computer (including the monitor) is turned on for 8.0 hours per day. If electricity costs 10¢ per kWh, how much does it cost to run the computer annually for a typical 365-day year? A) $120 B) $1200 C) $15 D) $17 E) $150

$120

The emf and the internal resistance of a battery are shown in the figure. If a current of 7.8 A is established through the battery from b to a, what is the terminal voltage Vab of the battery?

-30V

The resistivity of gold is 2.44 × 10-8 Ω · m at room temperature. A gold wire that is 1.8 mm in diameter and 11 cm long carries a current of 170 mA. How much power is dissipated in the wire? A) 0.030 mW B) 0.0076 mW C) 0.013 mW D) 0.019 mW E) 0.025 mW

.030 mW

For the circuit shown in the figure, what is the current through resistor R1?

.071A

When a 20.0-ohm resistor is connected across the terminals of a 12.0-V battery, the voltage across the terminals of the battery falls by 0.300 V. What is the internal resistance of this battery? A) 3.60 Ω B) 1.56 Ω C) 0.98 Ω D) 0.30 Ω E) 0.51 Ω

.51 ohms

Three resistors having resistances of 4.0 Ω, 6.0 Ω, and 10.0 Ω are connected in parallel. If the combination is connected in series with an ideal 12-V battery and a 2.0-Ω resistor, what is the current through the 10.0-Ω resistor? Chapter 25: Electric Circuits A) 0.59 A B) 2.7 A C) 6.4 A D) 11.2 A E) 16 A

.59A

Four resistors are connected across an 8-V DC battery as shown in the figure. The current through the 9-Ω resistor is closest to ) 1 A. B) 0.7 A. C) 0.5 A. D) 0.9 A. E) 2 A

.7 A

A 5.0-Ω resistor and a 9.0-Ω resistor are connected in parallel. A 4.0-Ω resistor is then connected in series with this parallel combination. An ideal 6.0-V battery is then connected across the series-parallel combination of the three resistors. What is the current through (a) the 4.0-Ω resistor? (b) the 5.0-Ω resistor? (c) the 9.0-Ω resistor?

.83A,.53A, .30A

In the figure a current of 6.0 A is drawn from the battery. What is the terminal voltage Vab of the battery?

0.00V

The resistivity of gold is 2.44 × 10-8 Ω · m at room temperature. A gold wire that is 0.9 mm in diameter and 14 cm long carries a current of 940 mA. What is the electric field in the wire? A) 0.036 V/m B) 0.0090 V/m C) 0.028 V/m D) 0.046 V/m E) 0.090 V/m

0.036 V/m

A silver wire with resistivity 1.59 × 10-8 Ω · m carries a current density of 4.0 A/mm2. What is the magnitude of the electric field inside the wire? A) 0.064 V/m B) 2.5 V/m C) 0.040 V/m D) 0.10 V/m

0.064 V/m

A cylindrical wire of radius 2.0 mm carries a current of 2.5 A. The potential difference between points on the wire that are 46 m apart is 3.7 V. (a) What is the electric field in the wire? (b) What is the resistivity of the material of which the wire is made?

0.080 V/m, 4.0 × 10-7 ohms*m

A certain fuse ʺblowsʺ if the current in it exceeds 1.0 A, at which instant the fuse melts with a current density of620 A/cm2. What is the diameter of the wire in the fuse?

0.45 mm

What must be the diameter of a cylindrical 120-m long metal wire if its resistance is to be 6.0 Ω? The resistivity of this metal is 1.68 × 10-8 Ω · m. A) 0.065 mm B) 0.65 mm C) 0.65 cm D) 0.325 mm E) 0.0325 mm

0.65 mm

A 150 watt light bulb is plugged into a 120 volt circuit. What current in A flows through the bulb? a. 10000 b. 0.8 c. 1.25 d. 0.08 e. 0.125

1.25

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 × 10-19 C) A) 1.6 × 1018 B) 1.6 × 1017 C) 1.5 × 1023 D) 3.7 × 1015 E) 6.3 × 1015

1.6*1018

For the circuit shown in the figure, determine the current in (a) the 7.0-Ω resistor. (b) the 8.0-Ω resistor. (c) the 4.0-Ω resistor.

1.6A,1.3A, .28A

A 110-V hair dryer is rated at 1200 W. What current will it draw when operating from a 110-V electrical outlet? A) 90 mA B) 1.0 A C) 5.0 A D) 11 A E) 14 A

11 A

A light bulb is connected to a 110-V source. What is the resistance of this bulb if it is a 100-W bulb? A) 100 Ω B) 8.0 mΩ C) 6.0 mΩ D) 120 Ω E) 240 Ω

120 ohms

How much current will be flowing through a 40.0 m length of cylindrical metal wire with radius 0.0 mm if it is connected to a source supplying 16.0 V? The resistivity of this metal is 1.68 × 10-8 Ω · m. A) 1200 A B) 9.5 × 108 A C) 68 nAD) 710 A

1200

The voltage and power ratings of a particular light bulb, which are its normal operating values, are 110 V and 60 W. Assume the resistance of the filament of the bulb is constant and is independent of operating conditions. If the light bulb is operated with a current that is 50% of the current rating of the bulb, what is the actual power drawn by the bulb? A) 10 W B) 15 W C) 20 W D) 25 W E) 30 W

15W

What length of a certain metal wire of diameter 0.15 mm is needed for the wire to have a resistance of 15 /30 Ω? The resistivity of this metal is 1.68 × 10-8 Ω · m. A) 16 mm B) 16 cm C) 1.6 m D) 16 m E) 160 m

16m/32m

The power rating of a 400-Ω resistor is 0.800 W. (a) What is the maximum voltage that can be applied across this resistor without damaging it? (b) What is the maximum current this resistor can draw without damaging it?

17.9V, 44.7mA

A tube of mercury with resistivity 9.84 × 10-7 Ω · m has an electric field inside the column of mercury of magnitude 23 N/C that is directed along the length of the tube. How much current is flowing through this tube if its diameter is 1.0 mm? A) 18 A B) 180 A C) 29 A D) 280 A

18 A

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) 2A. D) 3A. E) 18A.

18A

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

190 nA

A certain electric furnace consumes 24 kW when it is connected to a 240-V line. What is the resistance of the furnace? A) 1.0 kΩ B) 10 Ω C) 2.4 Ω D) 0.42 Ω E) 100 Ω

2.4 ohms

Nichrome wire, often used for heating elements, has resistivity of 1.0 × 10-6 Ω · m at room temperature. What length of No. 30 wire (of diameter 0.250 mm) is needed to wind a resistor that has 50 ohms at room temperature? A) 3.66 m B) 2.45 m C) 0.61 m D) 6.54 m E) 22.4 m

2.45m

For the circuit shown in the figure, determine the current in (a) the 1.0-Ω resistor. (b) the 3.0-Ω resistor. (c) the 4.0-Ω resistor.

2.8A,1.2A,.90A

When a voltage difference is applied to a piece of metal wire, a 5.0-mA current flows through it. If this metal wire is now replaced with a silver wire having twice the diameter of the original wire, how much current will flow through the silver wire? The lengths of both wires are the same, and the voltage difference remains unchanged. (The resistivity of the original metal is 1.68 × 10-8 Ω · m, and the resistivity of silver is 1.59 × 10-8 Ω · m.) A) 21 mA B) 19 mA C) 11 mA D) 5.3 mA

21 mA

For the circuit shown in the figure, I = 0.50 A and R = 12 Ω. What is the value of the emf ε?

24V

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 × 10-19 C) A) 0.20 B) 20 C) 2.0 D) 3.1 x 1020 E) 31 x 1020

3.1*1020

For the circuit shown in the figure, all quantities are accurate to 3 significant figures. What is the power dissipated in the 2-Ω resistor? A) 5.33 W B) 8.0 W C) 6.67 W D) 2.67 W E) 3.56 W

3.56W

A 2.0 mm diameter wire of length 20 m has a resistance of 0.25 Ω. What is the resistivity of the wire? A) 5.0 × 10-7 Ω · m B) 3.9 × 10-8 Ω · m C) 4.0 × 10-7 Ω · m D) 16 × 10-8 Ω · m E) 0.25 Ω · m

3.9*10^-8 ohms*m

When four identical resistors are connected to an ideal battery of voltage V = 10 V as shown in the figure, the current I is equal to 0.20 A. What is the value of the resistance R of the resistors? A) 20 Ω B) 40 Ω C) 30 Ω D) 50 Ω E) 10 Ω

30 ohms

How much energy in J is dissipated as heat during a two-minute time interval by a 1.5 kW resistor that has a constant 20 V potential difference across its leads? a. 58 b. 46 c. 32 d. 72 e. 16

32

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

33g

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) 17.5 A B) 30.9 A C) 61.8 A D) 388 mA E) 776 mA

388 mA

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?

39.6C

A galvanometer G has an internal resistance rg. An AMMETER is constructed by incorporating the galvanometer and an additional resistance Rs. Which one of the figures below is the most appropriate circuit diagram for the ammeter? Voltmeter?

4,1

The emf and the internal resistance of a battery are as shown in the figure. If a current of 8.3 A is drawn from the battery when a resistor R is connected across the terminals ab of the battery, what is the power dissipated by the resistor R? A) 440 W B) 700 W C) 620 W D) 530 W E) 790 W

440W

In the figure, when the terminal voltage Vab of the battery is equal to 20 V, how much current passes through the battery, including its direction?

4A, a-b

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

4I

What is the maximum current that can be drawn from a 1.50-V battery with an internal resistance of 0.30 ohm? A) 2.5 A B) 5.0 A C) 0.45 A D) 0.20 A E) 4.5 A

5.0A

A 4.0-mF capacitor is discharged through a 4.0-kΩ resistor. How long will it take for the capacitor to lose half its initial stored energy? A) 9.2 s B) 2.7 s C) 10.2 s D) 5.5 s E) 1.6 s

5.5s

The emf and the internal resistance of a battery are as shown in the figure. When the terminal voltage Vab is equal to 17.4 V, what is the current through the battery, including its direction? A) 6.8 A, from b to a B) 8.7 A, from b to a C) 6.8 A, from a to b D) 8.7 A, from a to b E) 16 A, from b to a

6.8A, b-a

If a current of 2.4 A is flowing in a cylindrical wire of diameter 2.0 mm, what is the average current density in this wire?

7.6 × 105 A/m2

The heater element of a particular 120-V toaster is a 8.9-m length of nichrome wire, whose diameter is 0.86 mm. The resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 Ω · m. If the toaster is operated at a voltage of 120 V, how much power does it draw? A) 720 W B) 700 W C) 750 W D) 770 W E) 800 W

720W

The voltage and power ratings of a particular light bulb, which are its normal operating values, are 110 V and 60 W. Assume the resistance of the filament of the bulb is constant and is independent of operating conditions. If the light bulb is operated at a reduced voltage and the power drawn by the bulb is 36 W, what is the operating voltage of the bulb? A) 66 V B) 72 V C) 78 V D) 85 V E) 90 V

85V

For the circuit shown in the figure, the current in the 8-Ω resistor is 0.50 A, and all quantities are accurate to 2 significant figures. What is the current in the 2-Ω resistor? A) 2.25 A B) 0.75 A C) 4.5 A D) 9.5 A E) 6.4 A

9.5 A

When a 100-Ω resistor is connected across the terminals of a battery of emf ε and internal resistance r, the battery delivers 0.794 W of power to the 100-Ω resistor. When the 100-Ω resistor is replaced by a 200-Ω resistor, the battery delivers 0.401 W of power to the 200-Ω resistor. What are the emf and internal resistance of the battery?

9V, 1.01 ohms

If the current density in a wire or radius R is given by J = kr, 0 < r < R, what is the current in the wire? A) 2πkR3/3 B) 3πkR3/2 C) kR3/3 D) kR2 E) kR2/2

A

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) True B) False

B

A cylindrical wire has a resistance R and resistivity ρ. If its length and diameter are BOTH cut in half, (a) what will be its resistance? You A) 4R B) 2R C) R D) R/2 E) R/4 (b) what will be its resistivity? A) 4ρ B) 2ρ C) ρ D) ρ/2 E) ρ/4

B,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.) A) The same current flows through both cables. B) Both cables carry the same current density. C) Theelectronshavethesamedriftvelocityinbothcables.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.

B,C

A wire of resistivity ρ must be replaced in a circuit by a wire of the same material but 4 times as long. If, however, the resistance of the new wire is to be the same as the resistance of the original wire, the diameter of the new wire must be A) the same as the diameter of the original wire. B) 1/2 the diameter of the original wire.C) 1/4thediameteroftheoriginalwire. D) 2 times the diameter of the original wire. E) 4 times the diameter of the original wire.

D

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.

E