Electricity and magnetism ( word problems )

In summary: However, if you stay in your car, the current will eventually kill you because the voltage will never go away. Nope. Let's say you are driving your car, and a power pole falls over next to you and the energized power wires lay across your car. Should you get out of your car and run away?No. There is a current flowing through the wires, but it will eventually die down. However, if you stay in your car, you could potentially get electrocuted.
  • #1
chipM
20
0

Homework Statement



please cheack my answears and see if they are right, please help me solve the wrong ones

thankyou !
(1)if you were to expend 10 J of work to push a 1 C charge against an electric field , what would be its change of Voltage ?

voltage = electric potential energy / charge

10/6.25x10^18

=1.6x10^-18 V

(2)(why is it safe to remain inside a car during a lightning storms?)

since like charges repel the electrons on the metal surface repel electrons of the lightining bolt hence its safe .

(3)your elcetronics friend needs a 20 ohm resistor and only has 40 ohm resistors , how can he combine them to produce a 20 ohm resistor ?

by putting them in parallel

(4)when preparing to undergo an MRI scan, why are patients advised to remove eyeglass watches jewlarry and other metal objects ?

(seriosuly i got no clue for this , maybe a hint? or two ? )

Homework Equations





The Attempt at a Solution

 
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  • #2
On #2 -- Your answer is not correct. Think about it some more and try again? You can probably even use Google to help you figure it out.

on #4 -- How do MRI scans work? They don't use X-rays; what do they use instead?
 
  • #3
cool i am on it

is 1 and 3 correct though ?
 
  • #4
for 1 is it

If the vehicle is struck the charge would be distributed across the conductive surface so contact should not be made with the inside of the vehicle until it has been discharged?
 
  • #5
for 4)

they are told to remove their jewlarry because of the magnetic field which can attract metals and as a result can pose risk to the patient or anyone in the room as the object is forced to move to the centre of the Mr system ?
 
  • #6
chipM said:
for 1 is it

If the vehicle is struck the charge would be distributed across the conductive surface so contact should not be made with the inside of the vehicle until it has been discharged?
Not quite. There are two issues at work helping to protect the occupants. Read about Faraday Cage at wikipedia to see if it helps with one issue. The other has to do with how currents flow. What path does current seek out?

chipM said:
for 4)

they are told to remove their jewlarry because of the magnetic field which can attract metals and as a result can pose risk to the patient or anyone in the room as the object is forced to move to the centre of the Mr system ?

Sounds reasonable.
 
  • #7
chipM said:
cool i am on it

is 1 and 3 correct though ?

#1 looks right, but I didn't check the math. on #3, I'd be explicit on how many resistors he should put in parallel. The wording of the problem makes it sound like he could have more than 2 resistors...
 
  • #8
Regarding 2)

is it because the car spreads out the charge around the cars exterior , which cancels out the charge in the cars exterior ?
 
  • #9
chipM said:
Regarding 2)

is it because the car spreads out the charge around the cars exterior , which cancels out the charge in the cars exterior ?

Nope. Think more in terms of currents, rather than charges...
 
  • #10
chipM said:
cool i am on it

is 1 and 3 correct though ?

For 1 a volt is a Joule/Coulomb. The units you are giving the potential in are Joule/e where e is the charge of a single electron. Not volts.
 
  • #11
berkeman said:
Nope. Think more in terms of currents, rather than charges...

is it because of the change in magnetic field causes in induced voltage, this voltage opposes the supply voltage to slow the build of current. when current become constant here is no voltage . is this it ?
 
  • #12
chipM said:
is it because of the change in magnetic field causes in induced voltage, this voltage opposes the supply voltage to slow the build of current. when current become constant here is no voltage . is this it ?

Nope. Let's say you are driving your car, and a power pole falls over next to you and the energized power wires lay across your car. Should you get out of your car and run away?
 
  • #13
no because there is current outside .
 

What is the difference between electricity and magnetism?

Electricity and magnetism are both forms of energy, but they have different properties and behaviors. Electricity is the flow of electrons, while magnetism is the force created by moving electric charges. Additionally, electricity can exist without magnetism, but magnetism cannot exist without electricity.

How are electricity and magnetism related?

Electricity and magnetism are closely related and are often referred to as electromagnetism. When an electric current flows through a wire, it creates a magnetic field. Similarly, a changing magnetic field can induce an electric current in a wire.

What is the difference between AC and DC electricity?

AC (alternating current) electricity changes direction periodically, while DC (direct current) electricity flows in only one direction. AC electricity is commonly used for powering homes and businesses, while DC electricity is typically used in smaller electronic devices.

How do electric circuits work?

An electric circuit is a closed loop through which electricity can flow. It consists of a power source, such as a battery or generator, and wires connecting the source to various components, such as lights or motors. When the circuit is complete, the flow of electricity allows the components to function.

How do magnets attract and repel?

Magnets have two poles, north and south, and opposite poles attract while like poles repel. This is due to the alignment of electrons within the magnet, which create a magnetic field. When two magnets are brought together, their magnetic fields interact with each other to either attract or repel.

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