# AP Physics 2: 1.3 Object Interaction and Forces

AP Physics 2: 1.3 Object Interaction and Forces. What is the magnitude of the current L in the wire?

AP Physics 2 | Object Interaction and Forces |

Language | English Language |

Science Practice 2 | Using math appropriately |

### Transcript

is perfect for migration seasons you got following figure This

shows a simplified experiment The magnetic field is produced by

a long straight wire And the pigeons beak is treated

as a point charge of plus ten e at a

distance of six centimetres from the wire with the point

charge has a velocity of five meters per second and

is subject to a magnetic force of four times ten

to the negative Twenty second newtons what's the magnitude of

the current l in the wire His s subzero is

approximately twelve times ten to the negative seventh newtons per

ampere square and hear the potential answer Six Twelve eighteen

Twenty four a Wow Pigeons are more impressive than we

thought Well maybe we should stop calling them flying garbage

rats That seems kind of disrespect We need an equation

to find the current in this wire and we need

to figure it out from outside the wire itself Based

off of the magnetic field the current creates around the

wire Let's Scroll through the equations We have crammed into

our brain to see what would work Well The best

equation that used for this is the equation for the

magnitude of a magnetic field which equals that constant of

vacuum permitted ity times the current divided by two pi

times Distance Yeah all right But to use this equation

we first have to find the magnitude of the field

more scrolling Sometimes it feels like if we memorize one

more equation we won't have enough power left over to

remember our own name Okay we can use the equation

for the force of a magnetic field that equals charge

times velocity times the magnitude of the magnetic field right

there and with a little algebraic crust o change Oh

we see that the magnitude of the field equals the

force divided by the charge times the velocity Now we

have two equations that both equal the magnitude of the

magnetic field which means the equations also each other And

we can rearrange the equation to solve for the current

Well finally we can plug in the numbers and do

some math But hold on let's make things easy on

ourselves with a little rounding fir e the unit of

charge will round that up to two times ten to

the negative nineteenth coolum And for pie will round that

down to three Okay we can't stand me into his

patient any longer Let's all this already the current equals

two times pi three times the distance six times ten

to the negative second meters times the force which equals

four times ten to the negative twenty second newton's All

of that is divided by the quantity of charge ten

times two times ten to the negative nineteenth times the

velocity five meters per second time's the electric constant twelve

times ten to the negative seventh newtons per amber's square

But once we put all this together we find that

the current equals twelve amps making answer Be the winner

So we'll give credit where it's due pigeons have super

powered beaks Maybe that would be a cool superhero pigeon

boy able to sense magnetic fields with his known it 00:03:25.738 --> [endTime] is better than another spider man reboot Oh