Problem 1 (50 points)Electrostatic discharge and methods for its prevention

EECS 314 WINTER 2013 HOMEWORK 2

Scenario 1: Only the gentleman's body accumuated the static charge (due to the friction against the glass ball); the lady's body did not carry any charge.

Statement 1:The sparks would be equally strong if the glass ball wre replaced with a grounded copper ball.

Answer: False

Electrostatic charge can be created triboelectrically on conductors the same way it is created on insulators. As long as the conductor is isolated from other conductors or ground, the static charge will remain on the conductor. If the conductor is grounded the charge will easily go to ground. Or, if the charged conductor contacts or nears another conductor, the charge will flow between the two conductors.

Statement 2:It is important that, after walking across the carpet, the lady was standing on an insulating surface. If shewere standing on a dissipative linoleum floor, there would be no spark whatsoever, regardless of what the gentleman was doing.

Answer: True

As with the other two types of materials, charge can be generated triboelectrically on a static dissipative material. However, like the conductive material, the static dissipative material will allow the transfer of charge to ground or other conductive objects. The transfer of charge from a static dissipative material will generally take longer than from a conductive material of equivalent size. Charge transfers from static dissipative materials are significantly faster than from insulators, and slower than from conductors.

Statement 3:

would be no spark whatsoever, regardless of what the gentleman was doing (assume that he did not wearsuch a wristband).

Answer: False

Though the dissipative writstband provides a path for the current to flow, if the resistance provided by the glass ball-man system is less than accumulate on the glass ball and sparks will occur.

Statement 4:If the gentleman were wearing a dissipative wristband connected to the ground via a would be no spark whatsoever, regardless of what the lady was doing (assume that she did not wear sucha wristband).

Answer: True

Any charge accumulating on the gentleman would be dissipated throuth the wristband.

Statement 5:If both the lady and the gentleman were wearing dissipative wristbands connected to each other via a 1-

spark could occur.

Answer: True

The charge would be sent through the dissipative wristband.

Statement 6:The sparks would be larger if they repeated the experiment outdoors under a heavy rain.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to maintain the humidity above 30%. So with a heavy rain the humidity would definitely be above 30%.

Statement 7:It is important that the gentlemen was wearing silk stockings: if he were wearing cotton socks, there would be no spark.

Answer: True

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 8The sparks would probably get larger if - instead of silk - the gentleman were wearing wool socks or stockings.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 9To avoid or reduce sparks between other bodies, you would use an air ionizer.

Answer: True

According to According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to work under an air ionizer in low humidity conditions (required < 30%RH).

Statement 10It is important that the gentleman had his body suspended: if he were standing on the same carpet with the lady, there would be no sparks whatsoever (assume that the carpet is insulating).

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 11There would be no sparks if the gentleman were lying on a copper plate instead of the wooden board.

Answer: False

The higher the static protection of the workstaton the less sparks.

Statement 12No matter what the material of the board was used, the main thing is that the suspending ropes must be not conducting: suspend him with wires - and there will be no sparks whatsoever!

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 13Neither the material of the board nor the materials of the suspensions are of any importance: the main thing is whether the hook, which holds everything was grounded: ground the hook - and the public will

be disappointed, because there would be no sparks no matter what the experimentalists did.

Answer: False

Statement 14If everything were made of cotton - all of their clothes and footwear, the ball, the board (or hammock) and the suspending ropes, the carpet, etc., there would be no sparks whatsoever.

Answer: True

Statement 15If, instead of a lady's finger, the gentleman would bring his nose near a modern circuit board with MOSFETs, etc., this could cause irreparale damage to some of the electronic components.

Answer: True

Scenario 2: The gentleman's body accumulated no electric charge (the glass ball machine was ineffective); at the same time, the lady's body was charged due to walking across the carpet.

Statement 1:The sparks would be equally strong if the glass ball wre replaced with a grounded copper ball.

Answer: False

Electrostatic charge can be created triboelectrically on conductors the same way it is created on insulators. As long as the conductor is isolated from other conductors or ground, the static charge will remain on the conductor. If the conductor is grounded the charge will easily go to ground. Or, if the charged conductor contacts or nears another conductor, the charge will flow between the two conductors.

Statement 2:It is important that, after walking across the carpet, the lady was standing on an insulating surface. If shewere standing on a dissipative linoleum floor, there would be no spark whatsoever, regardless of what the gentleman was doing.

Answer: True

As with the other two types of materials, charge can be generated triboelectrically on a static dissipative material. However, like the conductive material, the static dissipative material will allow the transfer of charge to ground or other conductive objects. The transfer of charge from a static dissipative material will generally take longer than from a conductive material of equivalent size. Charge transfers from static dissipative materials are significantly faster than from insulators, and slower than from conductors.

Statement 3:

would be no spark whatsoever, regardless of what the gentleman was doing (assume that he did not wearsuch a wristband).

Answer: False

Though the dissipative writstband provides a path for the current to flow, if the resistance provided by the glass ball-man system is less than accumulate on the glass ball and sparks will occur.

Statement 4:If the gentleman were wearing a dissipative wristband connected to the ground via a would be no spark whatsoever, regardless of what the lady was doing (assume that she did not wear sucha wristband).

Answer: True

Any charge accumulating on the gentleman would be dissipated throuth the wristband.

Statement 5:If both the lady and the gentleman were wearing dissipative wristbands connected to each other via a 1-

spark could occur.

Answer: True

The charge would be sent through the dissipative wristband.

Statement 6:The sparks would be larger if they repeated the experiment outdoors under a heavy rain.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to maintain the humidity above 30%. So with a heavy rain the humidity would definitely be above 30%.

Statement 7:It is important that the gentlemen was wearing silk stockings: if he were wearing cotton socks, there would be no spark.

Answer: True

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 8The sparks would probably get larger if - instead of silk - the gentleman were wearing wool socks or stockings.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 9To avoid or reduce sparks between other bodies, you would use an air ionizer.

Answer: True

According to According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to work under an air ionizer in low humidity conditions (required < 30%RH).

Statement 10It is important that the gentleman had his body suspended: if he were standing on the same carpet with the lady, there would be no sparks whatsoever (assume that the carpet is insulating).

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 11There would be no sparks if the gentleman were lying on a copper plate instead of the wooden board.

Answer: False

The higher the static protection of the workstaton the less sparks.

Statement 12No matter what the material of the board was used, the main thing is that the suspending ropes must be not conducting: suspend him with wires - and there will be no sparks whatsoever!

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 13Neither the material of the board nor the materials of the suspensions are of any importance: the main thing is whether the hook, which holds everything was grounded: ground the hook - and the public will be disappointed, because there would be no sparks no matter what the experimentalists did.

Answer: False

Statement 14If everything were made of cotton - all of their clothes and footwear, the ball, the board (or hammock) and the suspending ropes, the carpet, etc., there would be no sparks whatsoever.

Answer: True

Statement 15If, instead of a lady's finger, the gentleman would bring his nose near a modern circuit board with MOSFETs, etc., this could cause irreparale damage to some of the electronic components.

Answer: True

Scenario 3: Both the gentleman's and the lady's bodies were significantly charged; the charges they carried were of opposite signs.

Statement 1:The sparks would be equally strong if the glass ball wre replaced with a grounded copper ball.

Answer: False

Electrostatic charge can be created triboelectrically on conductors the same way it is created on insulators. As long as the conductor is isolated from other conductors or ground, the static charge will remain on the conductor. If the conductor is grounded the charge will easily go to ground. Or, if the charged conductor contacts or nears another conductor, the charge will flow between the two conductors.

Statement 2:It is important that, after walking across the carpet, the lady was standing on an insulating surface. If shewere standing on a dissipative linoleum floor, there would be no spark whatsoever, regardless of what the gentleman was doing.

Answer: True

As with the other two types of materials, charge can be generated triboelectrically on a static dissipative material. However, like the conductive material, the static dissipative material will allow the transfer of charge to ground or other conductive objects. The transfer of charge from a static dissipative material will generally take longer than from a conductive material of equivalent size. Charge transfers from static dissipative materials are significantly faster than from insulators, and slower than from conductors.

Statement 3:

would be no spark whatsoever, regardless of what the gentleman was doing (assume that he did not wearsuch a wristband).

Answer: False

Though the dissipative writstband provides a path for the current to flow, if the resistance provided by the glass ball-man system is less than accumulate on the glass ball and sparks will occur.

Statement 4:If the gentleman were wearing a dissipative wristband connected to the ground via a would be no spark whatsoever, regardless of what the lady was doing (assume that she did not wear sucha wristband).

Answer: True

Any charge accumulating on the gentleman would be dissipated throuth the wristband.

Statement 5:If both the lady and the gentleman were wearing dissipative wristbands connected to each other via a 1-

spark could occur.

Answer: True

The charge would be sent through the dissipative wristband.

Statement 6:The sparks would be larger if they repeated the experiment outdoors under a heavy rain.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to maintain the humidity above 30%. So with a heavy rain the humidity would definitely be above 30%.

Statement 7:It is important that the gentlemen was wearing silk stockings: if he were wearing cotton socks, there would be no spark.

Answer: True

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 8The sparks would probably get larger if - instead of silk - the gentleman were wearing wool socks or stockings.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 9To avoid or reduce sparks between other bodies, you would use an air ionizer.

Answer: True

According to According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to work under an air ionizer in low humidity conditions (required < 30%RH).

Statement 10It is important that the gentleman had his body suspended: if he were standing on the same carpet with the lady, there would be no sparks whatsoever (assume that the carpet is insulating).

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 11There would be no sparks if the gentleman were lying on a copper plate instead of the wooden board.

Answer: False

The higher the static protection of the workstaton the less sparks.

Statement 12No matter what the material of the board was used, the main thing is that the suspending ropes must be not conducting: suspend him with wires - and there will be no sparks whatsoever!

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 13Neither the material of the board nor the materials of the suspensions are of any importance: the main thing is whether the hook, which holds everything was grounded: ground the hook - and the public will be disappointed, because there would be no sparks no matter what the experimentalists did.

Answer: False

Statement 14If everything were made of cotton - all of their clothes and footwear, the ball, the board (or hammock) and the suspending ropes, the carpet, etc., there would be no sparks whatsoever.

Answer: True

Statement 15If, instead of a lady's finger, the gentleman would bring his nose near a modern circuit board with MOSFETs, etc., this could cause irreparale damage to some of the electronic components.

Answer: True

Scenario 4: Both the gentleman's and the lady's bodies were significantly charged; their charges were of the same sign, and their electric potentials were nearly the same.

Statement 1:The sparks would be equally strong if the glass ball wre replaced with a grounded copper ball.

Answer: False

Electrostatic charge can be created triboelectrically on conductors the same way it is created on insulators. As long as the conductor is isolated from other conductors or ground, the static charge will remain on the conductor. If the conductor is grounded the charge will easily go to ground. Or, if the charged conductor contacts or nears another conductor, the charge will flow between the two conductors.

Statement 2:It is important that, after walking across the carpet, the lady was standing on an insulating surface. If shewere standing on a dissipative linoleum floor, there would be no spark whatsoever, regardless of what the gentleman was doing.

Answer: True

As with the other two types of materials, charge can be generated triboelectrically on a static dissipative material. However, like the conductive material, the static dissipative material will allow the transfer of charge to ground or other conductive objects. The transfer of charge from a static dissipative material will generally take longer than from a conductive material of equivalent size. Charge transfers from static dissipative materials are significantly faster than from insulators, and slower than from conductors.

Statement 3:

would be no spark whatsoever, regardless of what the gentleman was doing (assume that he did not wearsuch a wristband).

Answer: False

Though the dissipative writstband provides a path for the current to flow, if the resistance provided by the glass ball-man system is less than accumulate on the glass ball and sparks will occur.

Statement 4:If the gentleman were wearing a dissipative wristband connected to the ground via a would be no spark whatsoever, regardless of what the lady was doing (assume that she did not wear sucha wristband).

Answer: True

Any charge accumulating on the gentleman would be dissipated throuth the wristband.

Statement 5:If both the lady and the gentleman were wearing dissipative wristbands connected to each other via a 1-

spark could occur.

Answer: True

The charge would be sent through the dissipative wristband.

Statement 6:The sparks would be larger if they repeated the experiment outdoors under a heavy rain.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to maintain the humidity above 30%. So with a heavy rain the humidity would definitely be above 30%.

Statement 7:It is important that the gentlemen was wearing silk stockings: if he were wearing cotton socks, there would be no spark.

Answer: True

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 8The sparks would probably get larger if - instead of silk - the gentleman were wearing wool socks or stockings.

Answer: False

According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to wear natural fabric clothes instead of synthetics (cotton versus polyester)

Statement 9To avoid or reduce sparks between other bodies, you would use an air ionizer.

Answer: True

According to According to ESD_Fall_2004.pdf one of the ways to minimize potential for electrostatic voltage generation is to work under an air ionizer in low humidity conditions (required < 30%RH).

Statement 10It is important that the gentleman had his body suspended: if he were standing on the same carpet with the lady, there would be no sparks whatsoever (assume that the carpet is insulating).

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 11There would be no sparks if the gentleman were lying on a copper plate instead of the wooden board.

Answer: False

The higher the static protection of the workstaton the less sparks.

Statement 12No matter what the material of the board was used, the main thing is that the suspending ropes must be not conducting: suspend him with wires - and there will be no sparks whatsoever!

Answer: False

A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring ESD protective materials and personnel to the same electrical potential. All conductors int the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel.

Statement 13Neither the material of the board nor the materials of the suspensions are of any importance: the main thing is whether the hook, which holds everything was grounded: ground the hook - and the public will be disappointed, because there would be no sparks no matter what the experimentalists did.

Answer: False

Statement 14If everything were made of cotton - all of their clothes and footwear, the ball, the board (or hammock) and the suspending ropes, the carpet, etc., there would be no sparks whatsoever.

Answer: True

Statement 15If, instead of a lady's finger, the gentleman would bring his nose near a modern circuit board with MOSFETs, etc., this could cause irreparale damage to some of the electronic components.

Answer: True

Part 2 (20 points)

Getting ready to work with sensitive electronic equipment, you should know how to eliminate not only spectacular sparks, but all undesirable voltages. Apply your knowledge and list your recommendations on how to create a safe working environment free of any sparks. Specify the following:

The key ESD control elements comprising most workstations are a static dissipative worksurface, a means of grounding personnel (usually a wrist strap), a common grounding connection, and appropriate signage and labeling.

Wear natural fabric clothes instead of synthetics (cotton versus polyester). Roll up your sleeves. Best use an ESDC lab coat.

Typically, wrist straps are the primary means of controlling static charge on personne. When properly worn and connected to ground, a wrist strap keeps a person wearing it near ground potential.

Fabrics with woven carbon or wires, formulated plastics bleed off charges more slowly - does not allow 'sparks'. Won't allow charges to build up.

Do not bring noncondcutors and unnecessary items into the work area (packing foams, coffee cups, etc.)

Problem 2 Electric Safety (70 points)

1. What levels of electric current through the human body are generally considered deadly? (Check all that apply)a. 50A(b. 5A(c. 500 mAd. 50 mA(e. 5 mA

2. If the external electric current completely stops someone's heart, will the heart restart itself?a. Never happensb. May happen but don't count on it.(c. Most certainly, yes.

3. An electric shock across one hand (finger to finger or finger to thumb) is ..a. Impossibleb. Deadlyc. Painful but usually not lethal(d. May hurt and burn.(

4. An electric shock that throws a person across the room is...a. Impossible, except if a lightning bolt hits the person directlyb. Quite likely if the current flows from hand to footc. Unavoidable, even if the person wears shoes with insulating soles.d. None of the above.(

5. Amplifiersa. Are among the safest devices to work with: they will never hurt anyone.b. Can easily kll you, especially Class Dc. May be relatively safe but still require safe working practices.(

6. A 12V car batterya. Can never create a current through the human body, which would be high enough to cause any damage or pain.b. Can provide very high currents, up to 300A.c. If the skin is cut or punched, a 12-V battery is capable of sending through a human body a current thathurts a lot

7. A pair of telephone lines at 48Va. may carry high currents that can cause electric arc.b. If a metal tool falls on such lines, nothing happens.c. If a metal tool falls on such lines, it may vaporize splattering molten metal all around.(d. In case of an arc discharge, present the danger of extreme heat and may cause eye damage due to UV radiation.e. In case of an arc discharge, only the extreme heat is dangerous.

8. Metal watch bands or rings remain cool if caught across the terminals of a 12-V car batterya. Are safe.b. Get warm, but not too hot to burn the skin.c. Can be easily melted into flesh.

9. The survivor's tales about minor electric shocks, after which they could not let go of a hot wirea. Are nothing but exaggeration.b. Can be explained by the structure of the muscles in the human hand.(c. Are true but unexplainable.d. Teach us that panic increases the chance of dying.(

10. If, lacking proper equipment, how you have to touch a wire to determin whether it is hot (live, carrying voltage and current)?a. Very carefully touch it with your fingertipb. Never use your fingertip, because it can get dirty.c. Never use your fingertip, because you may grab the wire and be unable to let it go.(d. Use the back of you hand.(e. Do not use the back of your hand, because the skin there is very insensitive.

11. If you see someone who fell after being shocked with a hot wire, which he cannot let go, the wisest course of action is?a. Don't bother: he'll recover in a few minutes and would do everything himself; your uninvited help might only embarass him.b. First, turn the power off; then help the person.(c. Help him stand up, then walk to the main switch to turn off the power.d. Not to be scared of anything, just help him the best you can.e. Call 911; even if they arrive half an hour later, nothing happens.

12. Mains outlets (household voltage)a. Have killed people only in UK, Australia, and other countries where the mains carry 240Vb. Are totally safe at 120 V(US standard)c. Require extreme care, regardless of the voltage.(d. IN the US, can be repaired even under appied voltage.e. May cause electrocution, but such events are highly unlikely.

13. Metal rings, jewelry, etc....a. Can be worn casually, because they present no danger working with electricity.b. May lead to trouble if they get caught by metal parts and do not allow you to withdraw your had from the source of electric shock.(c. Help you divert the current from your body, because their electric resistance is lower. Even if a high current flows through it, the ring itself remains cool.d. May get extremely hot in the case of an arc discharge even at low voltages.e. Make you especially attractive when you work on an electric system of a voltage car, and are quite safe because it is only 12V.

14. Microwave ovens can be deadly.a. True(b. False

15. To make sure that capacitors in the power supply of your PC are discharged, do the followinga. Turn off the switch; you may start working on the guts of the PC right away.b. Turn off the switch and wait for 3-5 minutes.c. Disconnect the power cord from the wall outlet, you may start working on the guts of the PC right away.d. Disconnect the power cord from the wall outlet; hold the power button pressed for several seconds; watch for the fan of the power supply to stop.(

e. Don't worry: they never get charged thus are always harmless.

16. Car ingnition systems will most likely kill you if you touch its parts with bare hands.a. Trueb. False(

17. If you are in a vehicle that comes in contact with a live powr line (very high voltage, possibly ~ 500kV or more)a. Remain in the vehicle until you are sure that the power line is no longer live (high voltage has been disconnected from it.)(b. Get out of the vehicle as soon as possible, regardless of how exactly you step out of it.c. If you must get out of the vehicle, make sure that you jump so that your body does not touch the vehicle and the ground at the same time.(d. Do not touch any metal parts inside your vehicle, because they will be at teh high voltage that may shock you.

18. If you are caught in the middle of a thunderstorm,a. Don't panic; walk as usual.b. Make long strides: you'll get home sooner without putting yourself in unnecessary danger.c. Crouch low.(d. Shorter steps are safer, because the voltage difference between your feet gets smaller and less dangerous.(

19. The person most responsible for your own personal safety isa. You(b. Your bossc. Your advisord. Your Department Chaire. Your Dean.

20. The recommended safety credo is: If it cannot be done safely,a. Ask your boss for clarification and advice.b. Research the Internet to learn about the official rules.c. Only a brave person should dare do it.d. It need not be done.(e. Call 911.

Problem 2 Part 2 (20 points)Briefly explain:a) Under what conditions the 12-V car battery can be dangerous, despite its low voltage? From http://askville.amazon.com/dangerous-car-batteries/AnswerViewer.do?requestId=4217899 Automotive batteries are the lead-acid type. They are full of sulfuric acid, which is extremely caustic and causes severe chemical burns if not washed off immediately.

There is also danger from the accumulation of hydrogen gas, which is released from the battery whenit is working. A spark from an incorrectly connected jumper or charger cable can ignite the hydrogen, which may cause an explosion.

b.) Under what conditions the fact that electric resistance of the ground (soil, dirt) is not exactly zero canbe of life- and-death importance? In the case of a downed power line. If the distance between two ground contact poits (the downled cabel and the system ground) is small, there will be substantial voltage dropped along short distances between the two points. Therefore, a person standing on the ground between those two points will be in danger of receiving an electric shock by intercepting a voltage between their two feet.

(4)(4)

(2)(2)

(3)(3)

(1)(1)

(5)(5)

Problem 2 Part 3 (30 points)

This sketch shows a circuit, in which the human body is inadvertently connected to an electric circuit that includes: The voltage source Vs with its internal resistance Rs, and the terminals labeled H1 and LO, and The load resistor R. The resistance of the human body gets connected in parallel to the load so that current I2 flows through the body

First, consider a digital multimeter (DMM) used to measure resistances. Assume Vs = 1.5V and Rs =

Your answer: R =

Assuming that the human resistance is in place when the measurement is made and the average

The voltage drop across Rs is:

and since V = I*R the total current in the circuit is

or I = .1uANow since I = .1uA and the voltage across R is given as 1.485V we can calculate the value of R

1.485

under three conditions:

expected.

(3) When the student wetted his hands and touch the resistor's connectors again, the DMM displayed

Calculate the electric parameters of the studen'ts body: fill the table below.

Experimental conditions

Electric resistance of the student's

Voltage V across the student's body,volts

Current I2 through the student's body,mA

Was the current through the student's body dangerous?

Dry hands

Wet hands

For 1):

(15)(15)

(11)(11)

(9)(9)

(8)(8)

(13)(13)

(10)(10)

(7)(7)

(14)(14)

(12)(12)

(6)(6)

Rstudent1:=

For 2)

For 3)

1.5

(17)(17)

(20)(20)

(19)(19)

(16)(16)

(18)(18)

(21)(21)

(22)(22)

0.8981060403

0.8981060403

For 4)

0.8499927777

0.8499927777For 5)

For 6)

Between measurements (2) and (3), the DMM's readings changed by a factor of 2. Did the student's body resistance also change by a factor of 2?

No: The equivalent resistance is comprised of three resistors, two in parallel (R and Rstudent) and one in series (Rs), so there is not a direct proportionality between Req and Rstudent.

Problem 2 Part 3, continuedEventually, analyze a more dangerous case where the source Vs = 12V is a car battery that can provide very high currents, including I2 through the human body.

Calculate the range of the load resistances R such that the current I2 remains below the Let-Go thresholdeven in the worst-case scenario when both hands are as wet as immersed in water.

For the largest "safe" value of R, calculate the power in watts absorbed by this resistor and write whetheryou think it can get very hot within a few seconds.

Your result: Power = W.

Do you think it can get very hot within a few seconds?

Your answer:

Problem 3 (80 points) Power in MOSFET and its load resistorPart 1 (10 points)Consider the circuit shown on the diagram; use the file "Mosfet data 2012=09-18 RL=5 ohm-4"In this experiment, Vdd was maintained constant at ~6V.

Write out the algebraic equations for:1. The voltage across the load resistor R

2. The current I in the circuit

3. The effective (equivalent) resistance of the MOSFET (between terminals D, S)

4. The power absorbed by the load resistor

5. The power absorbed by the MOSFET itself (between terminals D,S)

Part 2 (45 points)Use EXCEL or another program, with which you are comfortable, to create the following plots. To avoid meaningless values in your calculations, use the highest recorded voltage VDS as the value of Vdd.

A. The conductance (reciprocal of equivalent resistance) of the MOSFET between terminals D and S, in siemens (1 siemens = 1/(1 ohm))

The following graph was produced using matlab:>> VGS = xlsread(filename,'A:A');>> VDS = xlsread(filename,'B:B');>> Vdd = 6.006693;>> R = 5;>> Rx = (VDS*R)/(Vdd - VDS);>> Rconductance = 1./Rx;>> plot(Rconductance,VGS)>> hold on>> xlabel('VGS (V)')>> ylabel('G (S)')>> title('Conductance vs VGS')>> grid on

B. The power absorbed by the load resistor, in watts.The following graph was produced using matlab and the following commands:>> PL = (Vdd - VDS).^2/R;>> plot(PL,VGS)>> hold on

>> xlabel('VGS (V)')>> ylabel('PL (W)')>> title('PL vs VGS')>> grid on

C. The power absorbed by the MOSFET itself (between terminals D and S), in watts.The following graph was produced using matlab and the following commands:>> PDS = (VDS.*(Vdd - VDS).^2)/R;>> plot(PDS,VGS)>> hold on>> xlabel('VGS (V)')>> ylabel('PDS (w)')>> title('PDS vs VGS')>> grid on