Question 1

What current is flowing in a resistor if 4.0 × 1016 electrons pass a point in the resistor in 0.50 s? (e = $1.60 \times 10 ^ { - 19 } \mathrm { C }$ )

Accepted Answer

A)  $6.3 \mathrm {~A}$ 
B)  $78 \mathrm {~A}$ 
C)  $0.013 \mathrm {~A}$ 
D)  $0.31 \mathrm {~A}$ 
A)  $6.3 \mathrm {~A}$ 
B)  $78 \mathrm {~A}$ 
C)  $0.013 \mathrm {~A}$ 
D)  $0.31 \mathrm {~A}$ C

Question 2

A 200-Ω resistor is rated at 1/4 W. What is the maximum current it can safely draw?

Accepted Answer

A)  $0.035 \mathrm {~A}$ 
B)  $0.25 \mathrm {~A}$ 
C)  $0.35 \mathrm {~A}$ 
D)  $50 \mathrm {~A}$ 
A)  $0.035 \mathrm {~A}$ 
B)  $0.25 \mathrm {~A}$ 
C)  $0.35 \mathrm {~A}$ 
D)  $50 \mathrm {~A}$ A

Question 3

How much current will flow through a 40.0-m length of metal wire with a radius of $0.0 \mathrm {~mm}$ if it is connected to a power source supplying $16.0 \mathrm {~V}$ ? The resistivity of the metal is $1.68 \times 10 ^ { - 8 } \Omega \cdot \mathrm { m }$.

Accepted Answer

A)  $0 \mathrm {~A}$ 
B)  $0 \mathrm {~A}$. 
C)  $0 \mathrm { nA }$ 
D)  $0 \times 10 ^ { 8 } \mathrm {~A}$ 
A)  $0 \mathrm {~A}$ 
B)  $0 \mathrm {~A}$. 
C)  $0 \mathrm { nA }$ 
D)  $0 \times 10 ^ { 8 } \mathrm {~A}$ B

Question 4

A platinum wire is used to determine the melting point of indium. The resistance of the platinum wire is $2.000 \Omega$ at $20 ^ { \circ } \mathrm { C }$ and increases to $3.072 \Omega$ as indium just starts to melt. What is the melting point of indium? The temperature coefficient of resistivity for platinum is $3.927 \times 10 ^ { - 3 } / \mathrm { C } ^ { \circ }$.

Accepted Answer

A)  $351 ^ { \circ } \mathrm { C }$ 
B)  $156 ^ { \circ } \mathrm { C }$ 
C)  $116 ^ { \circ } \mathrm { C }$ 
D)  $136 ^ { \circ } \mathrm { C }$ 
A)  $351 ^ { \circ } \mathrm { C }$ 
B)  $156 ^ { \circ } \mathrm { C }$ 
C)  $116 ^ { \circ } \mathrm { C }$ 
D)  $136 ^ { \circ } \mathrm { C }$

Question 5

A 25-m wire of diameter $0.30 \mathrm {~mm}$ draws $0.499 \mathrm {~A}$ when connected across a $3.0$ - $\mathrm { V }$ potential difference.
(a) What is the resistance of the wire?
(b) What is the resistivity of the material from which the wire is made?

Accepted Answer

The answer of A 25-m wire of diameter \(0.30 \mathrm...

Question 6

If the power rating of a $400 - \Omega$ resistor is $0.800 \mathrm {~W}$, what is the maximum voltage that can safely be connected across the resistor?

Accepted Answer

A)  $170 \mathrm {~V}$ 
B)  $17.9 \mathrm {~V}$ 
C)  $110 \mathrm {~V}$ 
D)  $1.80 \mathrm {~V}$ 
A)  $170 \mathrm {~V}$ 
B)  $17.9 \mathrm {~V}$ 
C)  $110 \mathrm {~V}$ 
D)  $1.80 \mathrm {~V}$

Question 7

The heating element of a toaster is a $5.4 - \mathrm { m }$ length of nichrome wire of diameter $0.48 \mathrm {~mm}$. The resistivity of nichrome at the operating temperature of the toaster is $1.3 \times 10 ^ { - 6 } \Omega \cdot \mathrm { m }$. The toaster is designed to operate at a voltage of $120 \mathrm {~V}$. How much power does it draw in normal operation?

Accepted Answer

A)  $380 \mathrm {~W}$ 
B)  $360 \mathrm {~W}$ 
C)  $410 \mathrm {~W}$ 
D)  $400 \mathrm {~W}$ 
E)  $370 \mathrm {~W}$ 
A)  $380 \mathrm {~W}$ 
B)  $360 \mathrm {~W}$ 
C)  $410 \mathrm {~W}$ 
D)  $400 \mathrm {~W}$ 
E)  $370 \mathrm {~W}$

Question 8

For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

Accepted Answer

A)  $1 / ($ potential) 
B)  potential 
C)  resistance 
D)  (potential) 2 
E)  $1 /$ (resistance) 
A)  $1 / ($ potential) 
B)  potential 
C)  resistance 
D)  (potential) 2 
E)  $1 /$ (resistance)

Question 9

A tube of mercury with resistivity $9.84 \times 10 ^ { - 7 } \Omega \cdot \mathrm { m }$ has a uniform electric field of $23 \mathrm {~N} / \mathrm { C }$ inside the mercury. How much current is flowing in the tube, if the radius of the tube is $0.495 \mathrm {~mm}$ ?

Accepted Answer

A)  $280 \mathrm {~A}$ 
B)  $18 \mathrm {~A}$ 
C)  $29 \mathrm {~A}$ 
D)  $180 \mathrm {~A}$ 
A)  $280 \mathrm {~A}$ 
B)  $18 \mathrm {~A}$ 
C)  $29 \mathrm {~A}$ 
D)  $180 \mathrm {~A}$

Question 10

The power rating of a $400 - \Omega$ resistor is $0.800 \mathrm {~W}$.
(a) What is the maximum safe voltage across this resistor?
(b) What is the maximum current the resistor can safely draw?

Accepted Answer

(a) 17.9 V

Question 11

The length of a certain wire is doubled and at the same time its radius is also doubled. What is the new resistance of this wire?

Accepted Answer

A)  It is $1 / 2$ as large. 
B)  It stays the same. 
C)  It is 4 times as large. 
D)  It is $1 / 4$ as large. 
E)  It is 2 times as large. 
A)  It is $1 / 2$ as large. 
B)  It stays the same. 
C)  It is 4 times as large. 
D)  It is $1 / 4$ as large. 
E)  It is 2 times as large.

Question 12

In an electroplating process, it is desired to deposit $40 \mathrm { mg }$ of silver on a metal part by using a current of $2.0 \mathrm {~A}$. How long must the current be allowed to run to deposit this much silver? The silver ions are singly charged, and the atomic mass of silver is $108 \mathrm {~g} / \mathrm { mol } . \left( e = 1.60 \times 10 ^ { - 19 } \mathrm { C } _ { \mathrm { A } } = \right.$ $6.02 \times 10 ^ { 23 }$ atoms $/ \mathrm { mol }$ )

Accepted Answer

A)  $20 \mathrm {~s}$ 
B)  $18 \mathrm {~s}$ 
C)  $16 \mathrm {~s}$ 
D)  $22 \mathrm {~s}$ 
A)  $20 \mathrm {~s}$ 
B)  $18 \mathrm {~s}$ 
C)  $16 \mathrm {~s}$ 
D)  $22 \mathrm {~s}$

Question 13

The temperature coefficient of resistivity of platinum is $3.9 \times 10 ^ { - 3 } / \mathrm { C } ^ { \circ }$. If a platinum wire has a resistance of $R$ at a temperature of $23 ^ { \circ } \mathrm { C }$, to what temperature must it be heated in order to double its resistance to $2 R$ ?

Accepted Answer

A)  $730 ^ { \circ } \mathrm { C }$ 
B)  $300 ^ { \circ } \mathrm { C }$ 
C)  $930 ^ { \circ } \mathrm { C }$ 
D)  $280 ^ { \circ } \mathrm { C }$ 
A)  $730 ^ { \circ } \mathrm { C }$ 
B)  $300 ^ { \circ } \mathrm { C }$ 
C)  $930 ^ { \circ } \mathrm { C }$ 
D)  $280 ^ { \circ } \mathrm { C }$

Question 14

What current is flowing in a wire if $0.67 \mathrm { C }$ of charge pass a point in the wire in $0.30 \mathrm {~s}$ ?

Accepted Answer

A)  $2.2 \mathrm {~A}$ 
B)  $0.20 \mathrm {~A}$ 
C)  $0.30 \mathrm {~A}$ 
D)  $0.67 \mathrm {~A}$ 
A)  $2.2 \mathrm {~A}$ 
B)  $0.20 \mathrm {~A}$ 
C)  $0.30 \mathrm {~A}$ 
D)  $0.67 \mathrm {~A}$

Question 15

A $1.0 - \mathrm { m }$ length of nichrome wire has a radius of $0.50 \mathrm {~mm}$ and a resistivity of $1.0 \times 10 ^ { - 6 } \Omega \cdot \mathrm { m }$. When this wire carries a current of $0.50 \mathrm {~A}$, what is the voltage across its ends?

Accepted Answer

A)  $1.6 \mathrm {~V}$ 
B)  $0.0030 \mathrm {~V}$ 
C)  $0.64 \mathrm {~V}$ 
D)  $0.32 \mathrm {~V}$ 
A)  $1.6 \mathrm {~V}$ 
B)  $0.0030 \mathrm {~V}$ 
C)  $0.64 \mathrm {~V}$ 
D)  $0.32 \mathrm {~V}$

Question 16

Copper wire #1 has a length $L$ and a radius $b$. Copper wire #2 has a length $2 L$ and a radius $2 b$. Which statement about the resistance across the ends of the wires is true?

Accepted Answer

A)  The resistance of wire #1 is equal to that of wire #2. 
B)  The resistance of wire #1 is half that of wire #2. 
C)  The resistance of wire $\# 1$ is twice as high as that of wire $\# 2$. 
D)  The resistance of wire #1 is four times higher than that of wire #2. 
A)  The resistance of wire #1 is equal to that of wire #2. 
B)  The resistance of wire #1 is half that of wire #2. 
C)  The resistance of wire $\# 1$ is twice as high as that of wire $\# 2$. 
D)  The resistance of wire #1 is four times higher than that of wire #2.

Question 17

An instrument is rated at $250 \mathrm {~W}$ if it is connected across a $120 - \mathrm { V }$ dc power supply.
(a) What current does it draw under normal operation?
(b) What is its resistance?
(c) How many kilowatt-hours does it use in a day if it is left on all the time?

Accepted Answer

The answer of An instrument is rated at \(250 \mathrm...

Question 18

A $5.0$-V battery storing $43.0$ kJ of energy supplies $1.5$ A of current to a circuit. How much energy does the battery have left after powering the circuit for $1.0$ h.?

Accepted Answer

A)  $41 \mathrm {~kJ}$ 
B)  $43 \mathrm {~kJ}$ 
C)  $27 \mathrm {~kJ}$ 
D)  $16 \mathrm {~kJ}$ 
A)  $41 \mathrm {~kJ}$ 
B)  $43 \mathrm {~kJ}$ 
C)  $27 \mathrm {~kJ}$ 
D)  $16 \mathrm {~kJ}$

Question 19

A 400-W computer (including its 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 365-day year?

Accepted Answer

A)  $\$ 1200$ 
B)  $\$ 150$ 
C)  $\$ 120$ 
D)  $\$ 15$ 
A)  $\$ 1200$ 
B)  $\$ 150$ 
C)  $\$ 120$ 
D)  $\$ 15$

Question 20

A carbon resistor has a resistance of $18 \Omega$ at a temperature of $20 ^ { \circ } \mathrm { C }$. What is its resistance at a temperature of $120 ^ { \circ } \mathrm { C }$ ? The temperature coefficient of resistivity for carbon is $- 5.0 \times 10 ^ { - 4 } / \mathrm { C } ^ { \circ }$.

Accepted Answer

A)  $16 \Omega$ 
B)  $15 \Omega$ 
C)  $18 \Omega$ 
D)  $17 \Omega$ 
A)  $16 \Omega$ 
B)  $15 \Omega$ 
C)  $18 \Omega$ 
D)  $17 \Omega$

Exam 18: Electric Currents

What current is flowing in a resistor if 4.0 × 1016 electrons pass a point in the resistor in 0.50 s? (e = 1.60×10−19C1.60 \times 10 ^ { - 19 } \mathrm { C }1.60×10−19C )

A 200-Ω resistor is rated at 1/4 W. What is the maximum current it can safely draw?

A 25-m wire of diameter 0.30 mm0.30 \mathrm {~mm}0.30 mm draws 0.499 A0.499 \mathrm {~A}0.499 A when connected across a 3.03.03.0 - V\mathrm { V }V potential difference. (a) What is the resistance of the wire? (b) What is the resistivity of the material from which the wire is made?

If the power rating of a 400−Ω400 - \Omega400−Ω resistor is 0.800 W0.800 \mathrm {~W}0.800 W , what is the maximum voltage that can safely be connected across the resistor?

For the graph shown in the figure, what physical quantity does the slope of the graph represent for a dc circuit?

The power rating of a 400−Ω400 - \Omega400−Ω resistor is 0.800 W0.800 \mathrm {~W}0.800 W . (a) What is the maximum safe voltage across this resistor? (b) What is the maximum current the resistor can safely draw?

The length of a certain wire is doubled and at the same time its radius is also doubled. What is the new resistance of this wire?

What current is flowing in a wire if 0.67C0.67 \mathrm { C }0.67C of charge pass a point in the wire in 0.30 s0.30 \mathrm {~s}0.30 s ?

Copper wire #1 has a length LLL and a radius bbb . Copper wire #2 has a length 2L2 L2L and a radius 2b2 b2b . Which statement about the resistance across the ends of the wires is true?

An instrument is rated at 250 W250 \mathrm {~W}250 W if it is connected across a 120−V120 - \mathrm { V }120−V dc power supply. (a) What current does it draw under normal operation? (b) What is its resistance? (c) How many kilowatt-hours does it use in a day if it is left on all the time?

A 5.05.05.0 -V battery storing 43.043.043.0 kJ of energy supplies 1.51.51.5 A of current to a circuit. How much energy does the battery have left after powering the circuit for 1.01.01.0 h.?

A 400-W computer (including its 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 365-day year?

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Filters

What current is flowing in a resistor if 4.0 × 1016 electrons pass a point in the resistor in 0.50 s? (e = $1.60 \times 10 ^ { - 19 } \mathrm { C }$ )

A 25-m wire of diameter $0.30 \mathrm {~mm}$ draws $0.499 \mathrm {~A}$ when connected across a $3.0$ - $\mathrm { V }$ potential difference. (a) What is the resistance of the wire? (b) What is the resistivity of the material from which the wire is made?

If the power rating of a $400 - \Omega$ resistor is $0.800 \mathrm {~W}$ , what is the maximum voltage that can safely be connected across the resistor?

The power rating of a $400 - \Omega$ resistor is $0.800 \mathrm {~W}$ . (a) What is the maximum safe voltage across this resistor? (b) What is the maximum current the resistor can safely draw?

What current is flowing in a wire if $0.67 \mathrm { C }$ of charge pass a point in the wire in $0.30 \mathrm {~s}$ ?

Copper wire #1 has a length $L$ and a radius $b$ . Copper wire #2 has a length $2 L$ and a radius $2 b$ . Which statement about the resistance across the ends of the wires is true?

An instrument is rated at $250 \mathrm {~W}$ if it is connected across a $120 - \mathrm { V }$ dc power supply. (a) What current does it draw under normal operation? (b) What is its resistance? (c) How many kilowatt-hours does it use in a day if it is left on all the time?

A $5.0$ -V battery storing $43.0$ kJ of energy supplies $1.5$ A of current to a circuit. How much energy does the battery have left after powering the circuit for $1.0$ h.?