# What is the resistance ?

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 1/9

HW5 Due: 11:59pm on Friday, November 2, 2018

You will receive no credit for items you complete after the assignment is due. Grading Policy

Exercise 26.2

A machine part has a resistor protruding from an opening in the side. This resistor is connected to three other resistors, as shown in the figure . An ohmmeter connected across and reads 2.00 .

Part A

What is the resistance of ?

Express your answer in ohms to two significant figures.

ANSWER:

Exercise 26.12

In the battery has emf 43.0 and negligible internal resistance. = 6.00 . The current through is 2.50 and the current

through = 5.10 .

X a b

Ω

X

= X Ω

V

R1 Ω R1 A R3 A

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 2/9

Part A

What is the resistance ?

Express your answer with the appropriate units.

ANSWER:

Part B

What is the resistance ?

Express your answer with the appropriate units.

ANSWER:

Exercise 26.24

The batteries shown in the circuit in the figure have negligibly small internal resistances.

Part A

Find the current through the 30.0 resistor.

ANSWER:

Part B

Find the current through the 20.0 resistor.

ANSWER:

R2

= R2

R3

= R3

Ω

= I A

Ω

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 3/9

Part C

Find the current through the 10.0 battery.

ANSWER:

Exercise 26.30

The 5.00- battery in is removed from the circuit and replaced by a 15.00- battery, with its negative terminal next to point . The rest of the circuit is as shown in the figure.

Part A

Find the current in the upper branch.

Express your answer with the appropriate units. Enter positive value if the current is to the left and negative value if the the current is to the right.

ANSWER:

Part B

Find the current in the middle branch.

Express your answer with the appropriate units. Enter positive value if the current is to the left and negative value if the the current is to the right.

ANSWER:

= I A

V

= I A

V

V b

= I

= I

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 4/9

Part C

Find the current in the lower branch.

Express your answer with the appropriate units. Enter positive value if the current is to the left and negative value if the the current is to the right.

ANSWER:

Part D

Find the potential difference of point relative to point .

Express your answer with the appropriate units.

ANSWER:

Exercise 26.32

In the circuit shown in the figure both batteries have insignificant internal resistance and the idealized ammeter reads 2.00 in the direction shown.

Part A

Find the emf of the battery.

ANSWER:

Part B

= I

Vab a b

= Vab

A

E

= E V

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 5/9

Is the polarity shown correct?

ANSWER:

RC Circuit and Current Conceptual Question

In the diagram below,the two resistors, and , are identical and the capacitor is initially uncharged with the switch open.

Part A

How does the current through compare with the current through immediately after the switch is first closed?

You did not open hints for this part.

ANSWER:

Part B

How does the current through compare with the current through a very long time after the switch has been closed?

You did not open hints for this part.

ANSWER:

yes

no

R1 R2

R1 R2

The current through the current through .R1

is greater than

is less than

is equal to

R2

R1 R2

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 6/9

Part C

How does the current through compare with the current through immediately after the switch is opened (after being closed a very long time)?

You did not open hints for this part.

ANSWER:

Exercise 26.50

A 16.0- capacitor is charged to a potential of 50.0 and then discharged through a 265- resistor.

Part A

How long does it take the capacitor to lose half of its charge?

Express your answer with the appropriate units.

ANSWER:

Part B

How long does it take the capacitor to lose half of its stored energy?

Express your answer with the appropriate units.

ANSWER:

Exercise 26.48

The current through the current through .R1

is greater than

is less than

is equal to

R2

R1 R2

The current through the current through .R1

is greater than

is less than

is equal to

R2

μF V Ω

= t

= t

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 7/9

A 1.70- capacitor is charging through a 14.0- resistor using a 12.0- battery.

Part A

What will be the current when the capacitor has acquired 1/4 of its maximum charge?

ANSWER:

Part B

Will it be 1/4 of the maximum current?

ANSWER:

Exercise 26.46

A resistor and capacitor are connected in series to an emf source. The time constant for the circuit is 0.780 .

Part A

A second capacitor, identical to the first, is added in series. What is the time constant for this new circuit?

Express your answer with the appropriate units.

ANSWER:

Part B

In the original circuit a second capacitor, identical to the first, is connected in parallel with the first capacitor. What is the time constant for this new circuit?

Express your answer with the appropriate units.

ANSWER:

Problem 26.38

μF Ω V

= I A

yes

no

s

= τ

= τ

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 8/9

Part A

A 4.0-μF capacitor that is initially uncharged is connected in series with a 4.0-k resistor and an ideal 17.0-V battery. How much energy is stored in the capacitor 17 ms after the battery has been connected?

ANSWER:

Problem 26.57

Part A

Find the potential of point with respect to point in the figure .

Express your answer using two significant figures.

ANSWER:

Part B

If points and are connected by a wire with negligible resistance, find the magnitude of the current in the 10.0 battery.

Express your answer using two significant figures.

ANSWER:

Ω

890 nJ

15,000 kJ

25 µJ

250,000 nJ

a b

= Vab V

a b V

= I A

11/30/2018 HW5

https://session.masteringphysics.com/myct/assignmentPrintView?displayMode=studentView&assignmentID=6893051 9/9

Problem 26.69

A resistor consumes electrical power when connected to an emf . When resistor is connected to the same emf, it consumes electrical power .

Part A

In terms of and , what is the total electrical power consumed when they are both connected to this emf source in parallel?

ANSWER:

Part B

In terms of and , what is the total electrical power consumed when they are both connected to this emf source in series?

ANSWER:

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R1 P1 E R2 P2

P1 P2

= Ptot

P1 P2

= Ptot