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Carbon-zinc dry cells (sometimes referred to as non-alkaline cells) have an emf of 1.54 V, and they are produced as single cells or in various combinations to form other voltages. (a) How many 1.54-V cells are needed to make the common 9-V battery used in many small electronic devices? (b) What is the actual emf of the approximately 9-V battery? (c) Discuss how internal resistance in the series connection of cells will affect the terminal voltage of this approximately 9-V battery.

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What is the output voltage of a 3.0000-V lithium cell in a digital wristwatch that draws 0.300 mA, if the cell’s internal resistance is 2 . 00 Ω size 12{2 "." "00" %OMEGA } {} ?

2.9994 V

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(a) What is the terminal voltage of a large 1.54-V carbon-zinc dry cell used in a physics lab to supply 2.00 A to a circuit, if the cell’s internal resistance is 0 . 100 Ω size 12{0 "." "100" %OMEGA } {} ? (b) How much electrical power does the cell produce? (c) What power goes to its load?

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What is the internal resistance of an automobile battery that has an emf of 12.0 V and a terminal voltage of 15.0 V while a current of 8.00 A is charging it?

0 . 375 Ω size 12{0 "." "375" %OMEGA } {}

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(a) Find the terminal voltage of a 12.0-V motorcycle battery having a 0 . 600-Ω size 12{0 "." "600"- %OMEGA } {} internal resistance, if it is being charged by a current of 10.0 A. (b) What is the output voltage of the battery charger?

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A car battery with a 12-V emf and an internal resistance of 0 . 050 Ω size 12{0 "." "050" %OMEGA } {} is being charged with a current of 60 A. Note that in this process the battery is being charged. (a) What is the potential difference across its terminals? (b) At what rate is thermal energy being dissipated in the battery? (c) At what rate is electric energy being converted to chemical energy? (d) What are the answers to (a) and (b) when the battery is used to supply 60 A to the starter motor?

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The hot resistance of a flashlight bulb is 2 . 30 Ω size 12{2 "." "30" %OMEGA } {} , and it is run by a 1.58-V alkaline cell having a 0 . 100-Ω size 12{0 "." "100"- %OMEGA } {} internal resistance. (a) What current flows? (b) Calculate the power supplied to the bulb using I 2 R bulb size 12{I rSup { size 8{2} } R rSub { size 8{"bulb"} } } {} . (c) Is this power the same as calculated using V 2 R bulb size 12{ { {V rSup { size 8{2} } } over {R rSub { size 8{"bulb"} } } } } {} ?

(a) 0.658 A

(b) 0.997 W

(c) 0.997 W; yes

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The label on a portable radio recommends the use of rechargeable nickel-cadmium cells (nicads), although they have a 1.25-V emf while alkaline cells have a 1.58-V emf. The radio has a 3 . 20-Ω size 12{3 "." "20"- %OMEGA } {} resistance. (a) Draw a circuit diagram of the radio and its batteries. Now, calculate the power delivered to the radio. (b) When using Nicad cells each having an internal resistance of 0 . 0400 Ω size 12{0 "." "0400" %OMEGA } {} . (c) When using alkaline cells each having an internal resistance of 0 . 200 Ω size 12{0 "." "200" %OMEGA } {} . (d) Does this difference seem significant, considering that the radio’s effective resistance is lowered when its volume is turned up?

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An automobile starter motor has an equivalent resistance of 0 . 0500 Ω size 12{0 "." "0500" %OMEGA } {} and is supplied by a 12.0-V battery with a 0 . 0100-Ω size 12{0 "." "0100"- %OMEGA } {} internal resistance. (a) What is the current to the motor? (b) What voltage is applied to it? (c) What power is supplied to the motor? (d) Repeat these calculations for when the battery connections are corroded and add 0 . 0900 Ω size 12{0 "." "0900" %OMEGA } {} to the circuit. (Significant problems are caused by even small amounts of unwanted resistance in low-voltage, high-current applications.)

(a) 200 A

(b) 10.0 V

(c) 2.00 kW

(d) 0 . 1000 Ω ; 80 . 0 A, 4 . 0 V, 320 W size 12{0 "." "1000" %OMEGA ;" 80" "." "0 A, 4" "." "0 V, 320 W"} {}

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A child’s electronic toy is supplied by three 1.58-V alkaline cells having internal resistances of 0 . 0200 Ω size 12{0 "." "0200" %OMEGA } {} in series with a 1.53-V carbon-zinc dry cell having a 0 . 100-Ω size 12{0 "." "100"- %OMEGA } {} internal resistance. The load resistance is 10 . 0 Ω size 12{"10" "." 0 %OMEGA } {} . (a) Draw a circuit diagram of the toy and its batteries. (b) What current flows? (c) How much power is supplied to the load? (d) What is the internal resistance of the dry cell if it goes bad, resulting in only 0.500 W being supplied to the load?

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(a) What is the internal resistance of a voltage source if its terminal voltage drops by 2.00 V when the current supplied increases by 5.00 A? (b) Can the emf of the voltage source be found with the information supplied?

(a) 0 . 400 Ω size 12{0 "." "400" %OMEGA } {}

(b) No, there is only one independent equation, so only r size 12{r} {} can be found.

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A person with body resistance between his hands of 10 . 0 k Ω size 12{"10" "." 0" k" %OMEGA } {} accidentally grasps the terminals of a 20.0-kV power supply. (Do NOT do this!) (a) Draw a circuit diagram to represent the situation. (b) If the internal resistance of the power supply is 2000 Ω size 12{"2000" %OMEGA } {} , what is the current through his body? (c) What is the power dissipated in his body? (d) If the power supply is to be made safe by increasing its internal resistance, what should the internal resistance be for the maximum current in this situation to be 1.00 mA or less? (e) Will this modification compromise the effectiveness of the power supply for driving low-resistance devices? Explain your reasoning.

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Electric fish generate current with biological cells called electroplaques, which are physiological emf devices. The electroplaques in the South American eel are arranged in 140 rows, each row stretching horizontally along the body and each containing 5000 electroplaques. Each electroplaque has an emf of 0.15 V and internal resistance of 0 . 25 Ω size 12{0 "." "25" %OMEGA } {} . If the water surrounding the fish has resistance of 800 Ω size 12{"800" %OMEGA } {} , how much current can the eel produce in water from near its head to near its tail?

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Integrated Concepts

A 12.0-V emf automobile battery has a terminal voltage of 16.0 V when being charged by a current of 10.0 A. (a) What is the battery’s internal resistance? (b) What power is dissipated inside the battery? (c) At what rate (in º C/min size 12{°"C/min"} {} ) will its temperature increase if its mass is 20.0 kg and it has a specific heat of 0 . 300 kcal/kg º C size 12{0 "." "300"" kcal/kg" cdot °C} {} , assuming no heat escapes?

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Unreasonable Results

A 1.58-V alkaline cell with a 0 . 200-Ω size 12{0 "." "200"- %OMEGA } {} internal resistance is supplying 8.50 A to a load. (a) What is its terminal voltage? (b) What is the value of the load resistance? (c) What is unreasonable about these results? (d) Which assumptions are unreasonable or inconsistent?

(a) –0.120 V

(b) - 1 . 41 × 10 2 Ω size 12{ +- 1 "." "41"´"10" rSup { size 8{-2} } %OMEGA } {}

(c) Negative terminal voltage; negative load resistance.

(d) The assumption that such a cell could provide 8.50 A is inconsistent with its internal resistance.

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Unreasonable Results

(a) What is the internal resistance of a 1.54-V dry cell that supplies 1.00 W of power to a 15 . 0-Ω size 12{"15" "." 0- %OMEGA } {} bulb? (b) What is unreasonable about this result? (c) Which assumptions are unreasonable or inconsistent?

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Questions & Answers

derivation of ohms law
Kazeem Reply
derivation of resistance
Kazeem
R=v/I where R=resistor, v=voltage, I=current
Kazeem
Electric current is the flow of electrons
Kelly Reply
is there really flow of electrons exist?
babar
Yes It exists
Cffrrcvccgg
explain plz how electrons flow
babar
if electron flows from where first come and end the first one
babar
an electron will flow accross a conductor because or when it posseses kinectic energy
Cffrrcvccgg
electron can not flow jist trasmit electrical energy
ghulam
free electrons of conductor
ankita
electric means the flow heat current.
Serah Reply
electric means the flow of heat current in a circuit.
Serah
What is electric
Manasseh Reply
electric means?
ghulam
electric means the flow of heat current in a circuit.
Serah
a boy cycles continuously through a distance of 1.0km in 5minutes. calculate his average speed in ms-1(meter per second). how do I solve this
Jenny Reply
speed = distance/time be sure to convert the km to m and minutes to seconds check my utube video "mathwithmrv speed"
PhysicswithMrV
why we cannot use DC instead of AC in a transformer
kusshaf Reply
becuse the d .c cannot travel for long distance trnsmission
ghulam
what is physics
Chiwetalu Reply
branch of science which deals with matter energy and their relationship between them
ghulam
Life science
the
what is heat and temperature
Kazeem Reply
how does sound affect temperature
Clement Reply
sound is directly proportional to the temperature.
juny
how to solve wave question
Wisdom Reply
I would like to know how I am not at all smart when it comes to math. please explain so I can understand. sincerly
Emma
Just know d relationship btw 1)wave length 2)frequency and velocity
Talhatu
First of all, you are smart and you will get it👍🏽... v = f × wavelength see my youtube channel: "mathwithmrv" if you want to know how to rearrange equations using the balance method
PhysicswithMrV
nice self promotion though xD
Beatrax
thanks dear
Chuks
hi pls help me with this question A ball is projected vertically upwards from the top of a tower 60m high with a velocity of 30ms1.what is the maximum height above the ground level?how long does it take to reach the ground level?
mahmoud
please guys help, what is the difference between concave lens and convex lens
Vincent Reply
convex lens brings rays of light to a focus while concave diverges rays of light
Christian
for mmHg to kPa yes
Matthew
it depends on the size
Matthew Reply
please what is concave lens
Vincent
a lens which diverge the ray of light
rinzuala
concave diverges light
Matthew
thank you guys
Vincent
A diverging lens
Yusuf
What is isotope
Yusuf
each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element. "some elements have only one stable isotope
Karthi
what is wire wound resistors?
Naveedkhan Reply
What are the best colleges to go to for physics
Matthew Reply
I would like to know this too
Trevor
How do I calculate uncertainty in a frequency?
Rebecca Reply
Calculate . ..
Olufunsho
Practice Key Terms 4

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Source:  OpenStax, College physics. OpenStax CNX. Jul 27, 2015 Download for free at http://legacy.cnx.org/content/col11406/1.9
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