ShmoopTube

00:00

Thank you We sneak and here's your shmoop too sure

00:05

brought to you by model airplanes model airplanes air pretty

00:08

cool but be a lot cooler with model laser cannons

00:13

Extreme firehawk four is on course for a sweeping victory

00:18

in the final race of the model airplane championship Firehawk

00:22

moves left overtakes moves right steadies goes up a little

00:26

and uh you've missed it A tree a twelve o'clock

00:31

All right violet runs over to inspect the damage She

00:33

vows to make extreme firehawk five better than ever before

00:37

starting with the dc motor that spins the propeller Simple

00:41

dc motor includes two permanent magnets that provide a uniform

00:44

magnetic field Be a current of i runs through the

00:48

loop which has with w and length hell The magnetic

00:52

forces acting on the loop make it turn between the

00:55

magnets what's the magnitude and direction of the magnetic force

01:00

experienced by side to their alright here the potential answer

01:08

Well what a shame about this plane But no doubt

01:10

the next incarnation of extreme fire rock will be a

01:13

real beat We just have to figure out where we

01:15

can buy some model laser cannons for that model plane

01:18

Alright the equation to figure out the magnetic force here

01:21

is f sub b equals b l i signed data

01:26

where l is the length of the wire eyes The

01:28

current b is the magnitude of the field And seita

01:32

is the angle between the current and the magnetic field

01:34

Well magnetic field lines run north to south so the

01:38

magnetic field runs upward In this case inside to the

01:41

current is running to the left So theta the angle

01:44

between i and b is ninety degrees there which means

01:49

that the sign of data here equals one right over

01:53

that from oregon ometer out of you or whatever And

01:55

that means the magnitude of the force on side two

01:58

equals the magnitude of the field times the current times

02:02

the links got it So option c and d are

02:06

definitely wrong Just cross him out Now we just have

02:08

to find the direction of the magnetic force Well we'll

02:11

use the right hand rule for that We'll point our

02:14

right thumb in the direction of the current which onside

02:17

to is headed toward the left When we curl our

02:20

fingers while we see that they had downward into the

02:24

page giving us the direction that the correct answer to

02:27

the question is a And be careful out there You

02:31

don't want to be the victim of the extreme firehawk 00:02:34.265 --> [endTime] kamikaze version

Full Transcript